N E B R A S K Aextensionpublications.unl.edu/assets/pdf/mp69.pdf · 2015-09-10 · Weaning date...

MP 69-A

1998Beef Cattle Report

Agricultural Research DivisionUniversity of Nebraska Cooperative ExtensionInstitute of Agriculture and Natural Resources

University of Nebraska-Lincoln

Table of Contents

FinishingSolvent-Extracted Germ Meal for Receiving Calves ................................ 48Solvent-Extracted Germ Meal, Corn Bran and Steep Liquor Blends

for Finishing Steers ............................................................................ 50Lipid Sources in Finishing Diets for Yearling Steers ................................ 54An Enzyme-Microbial Feed Product for Finishing Steers ......................... 56Lime Filtrate as a Calcium Source for Finishing Cattle ........................... 58Extended Grazing and Byproduct Diets in Beef Growing Finishing

Systems............................................................................................. 60Effect of Winter Gain on Summer Rate of Gain and Finishing

Performance of Yearling Steers .......................................................... 63Summer and Fall Forage Grazing Combinations: Five-Year Summary .... 66Metabolism and Digestibility of Corn Bran and Corn Steep Liquor/

Distillers Solubles .............................................................................. 69Effects of Feed Intake Variation on Acidosis and Performance of

Finishing Steers................................................................................. 71Observations on Acidosis Through Continual Feed Intake and Ruminal

pH Monitoring ................................................................................... 75Phosphorus Requirement of Finishing Yearlings ...................................... 78Use of the NRC Model for Predicting Nutrient Balances of Finishing

Cattle................................................................................................. 80Evaluation of 1996 NRC for Protein and Phosphorus Requirements

of Finishing Cattle ............................................................................. 84Nutrient Balance of Nitrogen, Organic Matter, Phosphorus and Sulfur

in the Feedlot ..................................................................................... 86Nutrient Balance on Nebraska Feedlots ................................................... 88

New Methods and TechnologyIn Situ Method for Estimating Forage Protein Degradability ................... 90

Beef ProductsTenderness and Retail Stability of Hydrodyne-Treated Beef .................... 92Dietary Calcium and Phosphorous: Relationship to Beef Tenderness

and Carcass Maturity ........................................................................ 94

N E

B R

A S

K A

Acknowledgments........................................................................................ 2

Cow/CalfSpring versus Summer Calving for the Nebraska Sandhills: Production

Characteristics..................................................................................... 3Performance of Summer- and Spring-Born Calves Finished as Calves or

Yearlings............................................................................................. 5Use of the NRC Model for Evaluating Nutrient Balances of Grazing

Beef Cattle .......................................................................................... 7Dried Poultry Waste as a Protein Supplement for Cows Grazing Winter

Forages...............................................................................................11Escape Protein Supplementation and Weaning Effects on Calves Grazing

Meadow Regrowth............................................................................ 14Calving Difficulty and Calf Response to Stress ........................................ 17Effect of Summer Grazing on Crude Protein and Digestibility of Winter

Diets of Cattle in the Nebraska Sandhills ........................................... 20Ruminal Degradation of Rubisco by Beef Cattle Grazing Switchgrass

and Big Bluestem .............................................................................. 21Evaluating Stress in Calves Weaned at Three Different Ages .................. 23Induction of Estrus in Anestrous Suckled Beef Cows .............................. 26A Novel Estrous Synchronization Program for Beef Cattle Using

Melengestrol Acetate......................................................................... 29Effects of Luteinizing Hormone Releasing Hormone Antagonist On The

Bovine Corpus Luteum ..................................................................... 33Regulation of LH Secretion by Progesterone in Heifers ........................... 35Prolonged Elevated Concentrations of Estradiol Do Not Affect

Conception Rates in Beef Cattle ........................................................ 38

GrowingEvaluation of Feather Meal for Calves Grazing Cornstalks ..................... 40Feather Meal as a Source of Sulfur Amino Acids for Growing Steers ...... 42Cull Dry Edible Beans in Growing Calf Rations ..................................... 43Comparative Calf Grazing of Corn and Soybean Residues ...................... 45

1998 Nebraska Beef Report —

ACKNOWLEDGMENTS

Appreciation is expressed to the following firms, associations, or agencies who provided grant support for research in the beefcattle program.

Biotal Inc., Eden Prairie, MNCargill Corn Milling, Blair, NECargill Molasses Liquid Products, Elk River, MNElanco Animal Health, Indianapolis, INFats and Proteins Research Foundation, Chicago, ILFort Dodge Animal Health, Overland Park, KSGarrison and Townsend Inc., Hereford, TXInterAg Inc., Hamilton, New ZealandMilton G. Waldbaum Co., Wakefield, NEMinnesota Corn Processors, Columbus, NEMoorman Manufacturing Co., Quincy, ILNature’s Way, Inc., Horton, KS

Nebraska Beef Council, Kearney, NENebraska Dept. of Agriculture, Lincoln, NENovus International, St. Louis, MONebraska Grain Sorghum Development, Utilizations, and

Marketing Board, Lincoln, NEPioneer Hi-Bred International, Inc., West Des Moines, IASoypass Royalty Funds, University of Nebraska, Lincoln, NEThe North Central Region Sustainable Agriculture Research

and Education Program, Lincoln, NEUSDA-NRI Competitive Grants ProgramU.S. Poultry and Egg Association, Atlanta, GAZinpro Mineral Corp., Edina, MN

Appreciation is also expressed for the following firms who provided products or services.

Cargill Corn Milling, Blair, NEChief Industries, Hastings, NEDarling International, Irving, TXElanco Animal Health, Indianapolis, INExcel Corp., Wichita, KSFort Dodge Animal Health, Overland Park, KSJ.M. Huber Corp., Quincy, ILHoechst Roussel Agri.-Vet, Somerville, NJHydrodyne, Inc., San Juan, PRInterAg Inc., Hamilton, New ZealandIowa Limestone Co., Des Moines, IA

Liquid Feed Commodities, Fremont, NEMerck AgVet Division, Rahway, NJMinnesota Corn Processors, Columbus, NEMoorman Manufacturing Co., Quincy, ILPharmacia & The Upjohn, Inc., Kalamazoo, MIRhone-Poulenc, Atlanta, GASanofi Animal Health, Inc., Overland Park, KSUSDA, ARS, Meat Science Research Laboratory,

Beltsville, MDUSDA, AMS, Washington, D.C.

Appreciation is also expressed to the following Research Technicians, Unit Managers and Crew involved in the ResearchPrograms at our various locations.

Agricultural Research & Development Center, IthacaBob Borweleit Allison MillerJeff Bergman Karl MolineDan Herold Ken RezacDon Kuszak Doug RudeenTerry Kamphaus Keith RuffDon McClure

Animal Science Department, LincolnRob Cooper Debra LambrechtGalen Erickson Brad LindseyKatherine Gilson Machele MillerD.J. Jordon Ken PearsonMark Klemesrud Mike Wehrman

Gudmundsen Sandhills Laboratory, WhitmanAndy Applegarth Troy SmithJacki Johnson June UeckertMick McFadden

Panhandle Research & Extension Center, ScottsbluffNabor GuzmanPaul McMillenBrad Van Pelt

West Central Research & Extension Center, North PlatteTom Arensdorf Rex DavisDave Colburn Russell Sandberg

It is the policy of the University of Nebraska-Lincoln not to discriminate on the basis of gender, age, disability, race,color, religion, marital status, veteran’s status, national or ethnic origin or sexual orientation.

— 1998 Nebraska Beef Report

Spring versus Summer Calving for the NebraskaSandhills: Production Characteristics

Greg LardyDon AdamsDick Clark

Terry KlopfensteinJackie Johnson

Andy Applegarth1

Summer calving reduced hayinputs necessary to maintain thecow herd by 1.5 tons/cow/year.

Summary

Effects of summer calving versustraditional spring calving were inves-tigated over three years. Calving dateswere: 1) March to April (beginningMarch 18) for spring calving and 2)mid-June to mid-August (beginningJune 18) for summer calving. Spring-born calves were weaned in October,while summer-born calves were weanedin November or January. Summer calv-ing cows were bred either on nativerange or subirrigated meadow. Birthweights were higher for summer-borncalves, although weaning weights werelower. Pregnancy rates for spring-calv-ing cows bred on native range weresimilar to summer-calving cows bredon subirrigated meadow or nativerange. Summer calving reduced theamount of hay necessary to winter thecow herd by about 3,150 lb/hd/year.The amount of supplement fed/cow/year was similar for spring and sum-mer calving cows. Summer calving

offers significant feed and labor sav-ings for cow-calf producers.

Introduction

Analysis of herds participating inthe Nebraska IRM project indicatedfeed costs were the largest portion ofthe total cost of cow-calf production,although these cost varied among herds.In order to increase profitability, pro-ducers must either reduce productioncosts without sacrificing production orincrease production without markedlyincreasing costs.

The major portion of grazing land inthe Nebraska Sandhills is native uplandrange, which is primarily warm-seasongrasses. These grasses are highest inquality in June, July, and August (1997Nebraska Beef Report pp. 3-5). Tradi-tional spring calving herds, however,calve in February, March and April inNebraska, when warm-season grassesare dormant and will not maintain alactating cow. Cows, therefore, are fedmeadow hay and supplement until turn-out to grass. Previous research indi-cates extending winter and/or springgrazing reduces the amount of hayfed and increases profitability (1993Nebraska Beef Report pp. 5-8). Thisinformation led to establishment of thesummer calving project.

Key components of the summer calv-ing system include: 1) cows have accessto vegetative forage for a short timeprior to calving; 2) reduced hay andsupplement cost since peak lactation

occurs on vegetative forage; 3) reducedcalf sickness and death loss during calv-ing since it occurs during a warm, drytime period rather than the late winter/early spring; 4) reduced labor, machin-ery and fuel inputs associated with feed-ing hay; and 5) different marketingalternatives for Sandhills ranches, in-cluding a backgrounded calf in Marchor April, a yearling in September orslaughter cattle in January.

The objectives of this research wereto: 1) compare the production traits ofspring and summer calving herds in theNebraska Sandhills, including birth andweaning weights and hay and supple-ment inputs; and 2) evaluate the effectof breeding on subirrigated meadow ornative range for summer calving cows.We hypothesized that while Novemberweaning would be beneficial to the lac-tating cow grazing winter range, Janu-ary weaning would be best for keepingcalf cost low. Spring born-calves wereweaned in mid-October.

Procedure

In 1993, a summer-calving herd wasinitiated at the University of Nebraska-Lincoln’s Gudmundsen Sandhills Labo-ratory. Cows previously maintained in atraditional spring-calving herd wereassigned randomly to be bred in Sep-tember and October for calving betweenmid-June and mid-August. Approxi-mately 130 cows are maintained in thesummer-calving cow herd, while 400

(Continued on next page)


cows are maintained in the spring-calv-ing herd. Each herd is based on MARCII composite breeding (1/4 Angus, 1/4Hereford, 1/4 Simmental, 1/4 Gelbvieh).

Table 1 shows the production calen-dars for the spring- and summer-calv-ing herds. Birth weight, weaning weight,pregnancy rate and feed input data fromthe spring- and summer-calving herdswere collected in 1994, 1995 and 1996.

Within the summer-calving herd, twograzing treatments, either native rangeor subirrigated meadow regrowth, wereimposed during the breeding season.

Two weaning date treatments wereimposed on the summer-calving herd.Early weaning occurred November 1,while late weaning occurred January10.

Because replicate spring- and sum-mer-calving herds were not maintainedduring the winter feeding period, feedinputs are simply reported and not sta-tistically analyzed. Generally, thespring-calving herd was fed hay fromJanuary through mid-May. The sum-mer-calving herd was managed on dor-mant winter range plus supplementthroughout the winter. Hay was fed tosummer-calving cows only during ex-tremely inclement weather.

Results

Birth weights were higher (P < .01)for the summer-calving herd comparedto the spring-calving herd (Table 2).Although birth weights were greater,we observed less dystocia with the sum-mer-calving cows than the spring-calv-ing cows. In addition, summer-calvingcows were checked less frequently dur-ing calving than spring calvers. Aver-age birth date for the spring-born calveswas March 30; for the summer-borncalves the average birth date was June29. Actual weaning weights were lowerfor early and late-weaned summer borncalves (P < .01) compared to spring-born calves. In addition, weaningweights at about the same day of age(i.e. October versus January) were alsolower for late-weaned summer-borncalves compared to spring-born calves(P = .06). Summer-born calves weanedearly had lower weaning weights thansummer-born calves weaned in January

Table 1. Production calendar for spring- and summer-calving herds at the Gudmundsen SandhillsLaboratory.

Summer calving

Spring calving Early wean Late wean

Calving dates March 18 - April 18 June 8 - August 8 June 15-August 15Breeding season June - July September-October September-OctoberWeaning date October 10 November 1 January 10

Table 2. Effect of calving and weaning date on birth weight, birth date, and weaning weight (threeyears).

Summer calving

Spring calving Early wean Late wean Contrast1

Birth weight (lb) 90.0 96.4 95.8 1,3Birth date (Julian date) 90.5 181.6 179.0 1,3Weaning weight (lb) 471.0 369.8 435.8 1,2,3

1Contrasts: 1, Spring vs. Summer Calving; 2, Early vs. Late-Weaned Summer-Born Calves; 3, Late-Weaned Summer-Born Calves vs. Spring-Born Calves.

Table 3. Effect of grazing native range or subirrigated meadow on cow weight change and bodycondition score change during the breeding season for summer calving cows.

Cow Weight Cow BCSTreatment Year Change Change

Native Range 1994 -10.8 -0.14Native Range 1995 -23.0 -0.90Native Range 1996 -27.2 +0.07Subirrigated Meadow 1994 45.5 +0.09Subirrigated Meadow 1995 10.7 -0.39Subirrigated Meadow 1996 97.1 0.08

(P < .05).Summer-calving cows were fed 30

lb of hay/cow/year compared to 3,182lb/cow/year for spring-calving cows.Similar amounts of protein supplementwas fed to summer- (131 lb/cow) andspring-calving cows (108 lb/cow) eachyear. Opportunities for reducing theamount of hay fed to spring-calvingherds exist (1993 Beef Report, pp. 3-5).Previous economic analysis of winter-ing systems for Sandhills cow herdsindicated that maximizing winter graz-ing while minimizing hay feeding re-sulted in higher profitability (1993 BeefReport, pp. 5-8).

Significant year-by-treatment inter-actions were detected for cow weightchange and cow body condition scorechange during the breeding season forsummer-calving cows bred onsubirrigated meadow or native range(Table 3). Generally, cows gainedweight while grazing subirrigatedmeadow and lost weight while grazing

native range. Condition score changeswere similar and mostly small duringthe breeding season, except in 1995when two fall snowstorms adverselyaffected cow performance. In 1994, nosnowfall was recorded during the breed-ing season and average temperatureswere 2.4oF above normal. During Sep-tember and October, 1995, 24 inches ofsnow fell and average temperatures were1.0oF below average.

Calf gains were higher on sub-irrigated meadow, compared to nativerange, during the breeding season (P =.03; Table 4). Pregnancy rates weresimilar (P = .25).

Pregnancy rates were similar forspring-calving cows bred on nativerange during June and July or summer-calving cows bred on either native rangeor subirrigated meadow during Sep-tember and October (Table 4).

Summer calving offers advantagesfor Sandhills cow-calf producers. Per-haps the most significant advantage is


the reduced amount of hay and labor forfeeding hay necessary to winter the cowherd. Summer-born calves weaned atthe same age as the spring-born calveswere 35 lb lighter at weaning. Savingsin feed costs, however, may offset theloss in weaning weight. In addition,January calf prices for the relevant

Table 4. Effect of grazing native range or subirrigated meadow during the breeding season on calfweight gains and pregnancy rate (three years).

Subirrigatedmeadow Native range P-Value

Calf Weight Gain (lbs) 143.6a 127.6b .03Pregnancy Ratec (%) 91.6 94.9 .25

a,bMeans in same row with different superscripts differ (P = .03).cSpring calving cow pregnancy rate = 94.6%.

weight of calves tend to be higher thanOctober prices. For the producer sellingweaned calves, January calf priceswould need to be only about 8% higherthan October prices for the summer-born calves to generate equal grossincome. In Nebraska, producers re-ceived an average of 7.8 percent more


for the relevant weight calves in Janu-ary than in October over the 10-yearperiod 1986-1995. Given the historicalprice differentials, summer- and spring-born calves will generate similar grossincome; therefore, cost savings due toreduced feeding of hay made the sum-mer-born system more profitable atweaning time.

1Greg Lardy, former graduate student; TerryKlopfenstein, Professor, Animal Science, Lincoln;Don Adams, Professor; Dick Clark, Professor; JackieJohnson, research technician, West Central Researchand Extension Center, North Platte; AndyApplegarth, ranch manager, Gudmundsen SandhillsLaboratory, Whitman.

Performance of Summer- and Spring-Born CalvesFinished as Calves or Yearlings

Greg LardyDon Adams

Richard ClarkTerry Klopfenstein1

Performance of summer- andspring-born calf-feds and yearlingfinishing systems will be affectedmore by seasonality of prices thanslaughter breakevens.

Summary

Performance of spring-born calf-fed, early weaned summer-born calf-fed, late-weaned summer-born calf-fed,early weaned summer-born yearlings,and late-weaned summer-born year-lings was evaluated in the two-yearstudy. Neither feeding nor carcasscharacteristics were influenced byweaning date. No weaning date bycalf management system interactions

were detected. Spring-born calf-feds had higher initial weights butsimilar final weights, compared tosummer-born calf-feds, and carcasscharacteristics of spring- and summer-calf-feds were similar. Yearlings hadhigher initial, final and hot carcassweights, higher dry matter intakes andpoorer feed efficiencies compared tosummer-born calf-feds. Slaughterbreakevens were similar among treat-ments.

Introduction

Calving date significantly impactsall aspects of cow-calf production, andis not limited simply to issues ofmatching forage resources to thecows’ nutrient requirements. To takeadvantage of the benefits of changingcalving dates, producers may need tochange marketing and calf manage-ment plans at weaning and post-weaning.

The objectives of this research wereto: 1) determine the effect of weaningdate on feedlot and carcass characteris-tics of summer-born steers; 2) deter-mine the effect of calf fed versus yearlingfeeding system on feedlot and carcasscharacteristics of summer-born steers;and 3) determine the effect of spring(March to April) versus summer (Juneto July) calving date on feedlot andcarcass characteristics of beef steers.

Procedure

Steers were produced at the Univer-sity of Nebraska’s GudmundsenSandhills Laboratory (GSL) and wereof MARC II breeding (1/4 Hereford,1/4 Angus, 1/4 Gelbvieh and 1/4 Sim-mental composite). Spring-born steerswere born beginning March 18, weanedabout October 10 and shipped to theUniversity of Nebraska-Lincoln’s feed-lot at Mead on November 15 in 1994and 1995.


Summer-born steers were born be-ginning June 18. Steers were weanedNovember 1 (early weaning) or January10 (late weaning). All steers werebackgrounded at GSL until February 14when steers designated for calf-fedtreatments were shipped to Mead forfeeding. Steers designated for yearlingtreatments remained at GSL throughthe winter, grazed native Sandhillsrange throughout the summer andwere shipped to the Mead feedlot onSeptember 10. Early and late-weanedyearling steers grazed in a commonpasture during the summer. Each calv-ing date-feeding system group was fedin two pens each year at Mead.

All steers were fed a common finish-ing diet (Table 1) based on a blend ofdry rolled corn and wet corn glutenfeed. Diets were formulated to containa minimum of 13% CP, .7% Ca, .35% Pand .7% K. All diets contained 25 g/tonRumensin® and 10 g/ton Tylan®. Steersfed as calf-feds were implanted twiceduring the finishing period withRevalor®; yearlings were implantedonce with Revalor® during the finish-ing period. Breakeven prices for fin-ished cattle were estimated by using1986-1995 average prices for westernNebraska feeder cattle.

Results

No interactions between weaningdate and steer feeding system were de-tected. Initial and final weights werehigher for summer-born yearlings ascompared to summer-born calf-feds(Table 2). In addition, initial weights ofthe spring-born calf-feds were higherthan summer-born calf-feds. However,the summer-born calf-feds compensatedover the feeding period and had similarfinal weights compared to spring-borncalf-feds. Average daily gains were simi-

Table 1. Composition of diet fed to spring andsummer-born steers (% DM basis).

Ingredient %

Dry Rolled Corn 50.0Wet Corn Gluten Feed 35.0Corn Silage 5.0Alfalfa Hay 5.0Supplement 5.0

Table 2. Initial weights, final live weights, hot carcass weights, average daily gains, dry matterintakes and feed efficiencies of spring-born steers and summer-born steers as influencedby weaning date and management strategy.

Summer-born steers

Calf-Fed YearlingSpring-born

calf-fed Early Late Early Late Contrasta

Initial weight 540 444 466 780 776 1, 2Final weight 1179 1146 1161 1283 1293 2ADG 3.8 3.9 3.9 4.1 4.2 NSDMI 20.8 20.6 21.3 26.1 26.8 2Feed/Gain 5.5 5.3 5.6 6.4 6.4 2Days on feed 171 181 181 124 124 2

aContrasts: 1, spring vs. summer calf-feds; 2, Summer-born calf-feds vs. summer-born yearlings.

Table 3. Carcass characteristics of spring-born steers and summer-born steers as influenced byweaning date and management strategy.

Summer-born steers


calf-fed Early Late Early Late Contrasta

Hot carcass weight 731 710 720 796 801.7 2Yield grade 2.0 1.9 1.9 2.0 2.24 NSRib eye area 13.5 14.1 13.7 14.2 14.3 NSQuality gradeb 18.0 17.9 17.8 18.8 18.2 2

aContrasts: 1, spring vs. summer calf-feds; 2, Summer-born calf-feds vs. summer-born yearlings.bQuality Grade: 17 = Select+; 18 = Choice-; 19 = Choice ; 20 = Choice+.

lar for calving date, weaning date andsteer feeding system.

Dry matter intakes were higher forsummer-born yearlings as compared tocalf-feds (Table 2). Feed-to-gain con-versions were poorer for the yearlingsthan the calf-feds, but not unexpected.No effect of weaning date was noted forany of the variables measured in thefeedlot. Steers from each weaning datewere slaughtered at the same time, con-sequently no differences were noted indays on feed for early and late-weanedsummer-born calves or yearlings.Spring-born and summer-born calf-fedswere fed for a similar amount of time,while yearlings had significantly fewerdays on feed.

Although yearlings had higher hotcarcass weights and higher qualitygrades compared to calf-feds (Table 3),no other differences were noted in car-cass characteristics.

Slaughter breakeven was not differ-ent for any birth date, weaning date ormanagement system treatment (Table

4). Since marketing dates for slaughtercattle will be different with the varioussystems, relative profitability of thesystems will be affected by sale price.Typically, seasonal prices for slaughtersteers are highest in April and lowest inAugust. In this trial, spring-born steerswere marketed in early May, summer-born calf-feds in August and summer-born yearlings in January. Theprofitability of the summer-born calf-fed system will likely be reduced due toseasonality in prices, not because ofslaughter breakevens. However, for theproducer who retains ownership, totalcost in summer-borns will be lower dueto lower costs of producing a weanedcalf.

Weaning date influenced neitherfeeding nor carcass characteristics ofsummer-born steers. Managing calvesfor slaughter as yearlings resulted inhigher initial, final and hot carcassweights, dry matter intakes and qualitygrades but poorer feed efficiency com-pared to calf-feds. No differences were


Table 4. Feed inputs and slaughter breakevens as influenced by birth date, weaning date andmanagement system.

Summer-born steers


calf-fed Early Late Early Late

Value of calf at weaninga, $ 397.43 360.31 396.89 360.31 396.89Feed Inputs prior to feedlot entryb, $ 21.15 45.37 21.15 118.03 75.74Summer grazingc, $ — — — 42.00 42.00

FeedlotFeedd, $ 174.90 185.85 192.14 160.55 164.64Yardagee, $ 52.22 54.08 54.08 37.38 37.38Healthf, $ 15.00 15.00 15.00 15.00 15.00

Interestg, $ 23.66 28.56 24.75 52.61 45.18Total costs, $ 684.37 689.20 704.02 785.88 776.84

Slaughter Breakeven, $/cwth 58.67 60.48 61.01 61.92 60.50aWeaning weight * price; Prices=$84.38 for Spring-born, $97.38 for Early Weaned Summer-Born and$91.03 for Late-Weaned Summer-Born.b$45/Ton for Meadow Hay and $170/Ton for Supplement.cGrazing Cost=$0.35/hd/day.dFeed Cost=$0.05/lb.eYardage=$0.30/hd/day.fIncludes parasite control, implants, etc.gInterest=8%/year.hNo significant (P<.05) differences.

noted in average daily gain or yieldgrade. Only initial weights were differ-ent when spring and summer calf-fedfinishing systems were compared.Slaughter breakevens were similar forall treatments.

Since neither date of birth nor wean-ing impacted feeding and carcass char-acteristics or slaughter breakevens ofcalf-feds, producers who retain owner-ship can base decisions regarding calv-ing date around marketing plans,seasonal price patterns and the impactof changing calving date on cow pro-ductivity.

1Greg Lardy, former research assistant, AnimalScience, Lincoln; Don Adams, Professor, AnimalScience, West Central Research and ExtensionCenter, North Platte; Richard Clark, Professor,Agricultural Economics, West Central Researchand Extension Center, North Platte; TerryKlopfenstein, Professor, Animal Science, Lincoln.

Use of the NRC Model for Evaluating NutrientBalances of Grazing Beef Cattle


Greg LardyDon Adams

Terry KlopfensteinDennis Brink1

The National Research CouncilModel is a useful tool for predict-ing nutrient balances of grazinganimals when accurate estimatesof digestibility, intake and proteindegradability are available.

Summary

Research conducted at the Gud-mundsen Sandhills Laboratory evalu-ated the National Research CouncilBeef Cattle Nutrient RequirementsModel. Equations describing seasonalvariability in CP, IVOMD, escape pro-tein and degradable intake proteinof native Sandhills range and

subirrigated meadow were developed.Estimates of TDN and proteindegradability for feedstuffs commonlyused by Nebraska cow-calf producersare given. The NRC Model generallypredicted nutrient balances in agree-ment with research trials. Microbialefficiency is lower for less-digestibleforages. The NRC model is useful forevaluating grazed diets when accurateestimates of protein degradability, di-gestibility and intake are available.

Introduction

Recently, the National ResearchCouncil revised its Nutrient Require-ments of Beef Cattle. One of the mostsignificant changes is the move fromexpressing protein requirements on acrude protein (CP) basis to a systemwhich uses degraded intake protein(DIP) and metabolizable protein (MP).Protein degraded in the rumen and avail-

able for use by the rumen microbes isreferred to as DIP, while MP is theprotein utilized by the host animal andis the sum of the digestible bacterialprotein produced in the rumen and thedigestible undegradable intake protein(UIP) from the feedstuffs consumed bythe animal. The CP system assumed,inaccurately, a constant degradabilityfor all feedstuffs.

The requirement for DIP is estimatedby multiplying TDN intake by micro-bial efficiency. Microbial efficiency,measure of the amount of TDN whichthe ruminal bacteria convert to micro-bial protein, is important. In the NRCmodel, microbial efficiency determinesthe amount of DIP required by the rumi-nal bacteria, as well as the amount ofMP supplied to the animal from bacte-rial fermentation in the rumen.

In order for the NRC model to accu-rately predict nutrient supply to the


animal, accurate estimates of digest-ibility, intake and protein degradabilityare necessary. For grazing animals, es-timates of protein degradability of thediet are lacking.

Our objectives were to: 1) reportprotein degradabilities for forages andother feedstuffs commonly used in Ne-braska; 2) demonstrate the importanceof microbial efficiency in determiningDIP and MP supplies; 3) use researchtrials previously conducted at Univer-sity of Nebraska’s GudmundsenSandhills Laboratory research facilitiesto evaluate the NRC model; and 4)present guidelines for successful use ofthe NRC Model.

Procedure

Research trials previously conductedat the University of Nebraska’sGudmundsen Sandhills Laboratory wereused as validation data sets. Refer toprevious Nebraska Beef Reports citedin the discussion of each respectivevalidation for complete information onsupplements, cattle management andother items related to each trial. Forpurposes of calculating NE

m balances,

in vitro organic matter digestibility(IVOMD) values for supplements andforages were assumed to be equal toTDN.

The PROC REG procedures of SASwere used to develop multiple regres-sion equations for prediction of CP,DIP, escape protein (EP; equivalent toUIP) and IVOMD for native uplandrange and subirrigated meadow. Be-cause a hierarchical model buildingprocess was used, all lower-order termswere included when a higher-orderterm was included in the model (e.g. ifX3 was significant, X and X2 wereincluded as well).

Results

Table 1 shows the means and stan-dard deviations in nutritive value forSandhills range and meadow diets col-lected with esophageally cannulatedcows. The values shown are means ofdiets collected on native winter range,summer native range and subirrigatedmeadow regrowth during 1992 and 1994

Table 2. Regression equations to predict crude protein, escape protein, degradable intake proteinand in vitro organic matter disappearance of subirrigated meadow and native rangesamples.

Subirrigated meadowNutrienta Equationb R2

CP (% of OM) 1.523698 +1.346704Z -0.024693Z2 .651+(1.77324 x 10-4)Z3 -(5.54 x 10-7)Z4

-(6.27927 x 10-10)Z5

UIP (% of OM) -4.98141 +0.543179Z -0.011468Z2 .835(1.08125 x 10-4)Z3 -(5.11525 x 10-7)Z4

+(1.18228 x 10-9)Z5 -(1.06095 x 10-12)Z6

DIP (% of OM) 2.97353 +1.120967Z -0.021132Z2 .633+0.00015405Z3 -(4.860933 x 10-6)Z4

+(5.536177 x 10-10)Z5

IVOMD 65.14141 +0.53003Z -0.0003067465Z2 .477

Native upland range

Nutrienta Equationb R2

CP (% of OM) 11.119 +0.062249Z -0.0006297Z2 .660+(1.1781796 x 10-6)Z3

UIP (% of OM) 0.292825 +0.076754Z -0.000852403Z2 .823+(3.191545 x 10-6)Z3 -(3.90416 x 10-9)Z4

DIP (% of OM) 9.99572 +0.035668Z -0.0004266766Z2 .630+(8.168981 x 10-7)Z3

IVOMD 59.54957 +0.466131Z -0.005775681Z2 .686+(2.192993 x 10-5)Z3 -(2.665154 x 10-8)Z4

aCP, crude protein; UIP, undegraded intake protein; DIP, degraded intake protein; IVOMD, in vitroorganic matter disappearance.bZ=Day after April 1.

Table 1. Means + standard deviations of crude protein, protein degradability, digestibility, neutraldetergent fiber and acid detergent fiber of Nebraska Sandhills forages.

CP DIP NDF ADFForage (% of OM) (% of CP) IVOMD (% of OM) (% of OM)

Summer native range 12.5+2.39 82.3+2.49 66.4+3.37 77.0+4.81 43.6+4.45Winter native range 6.2+0.45 84.7+2.44 54.0+2.44 84.2+1.61 54.0+1.19Subirrigated meadow

regrowth 13.2+3.89 86.9+2.65 61.7+7.12 71.9+8.80 46.2+6.46

at the Gudmundsen Sandhills Labora-tory (1997 Nebraska Beef Report pp. 3-5). Meadow regrowth was most variablein CP, IVOMD and NDF. This may beexpected, since these diets coveredAugust through December, represent-ing high-quality regrowth immediatelyfollowing haying to dormant forage inearly winter. Degraded intake protein,when expressed as a percentage of crudeprotein, was similar for the three foragetypes and averaged 84.6%.

Regression equations for relating date

with CP, EP, DIP and IVOMD of nativerange and subirrigated meadow foragesare shown in Table 2. All equationsexplained at least 50% of the variationin nutrient content’s seasonal changes.The highest R2 values were obtained forEP for both native range and subirrigatedmeadow. These equations allow foragequality variables to be predicted for anyday of the year.

Table 3 shows the effect of changesin microbial efficiency on DIP and MPsupplies, requirements and balances for


ages which pass slower result in slowermicrobial growth, lowering both therequirement for DIP and the amount ofMP produced by the bacteria whichferment that forage. Forages which havehigher digestibilities result in moremicrobial growth which increases therequirement for DIP.

For cows grazing winter range andother low quality forages, we suggestusing microbial efficiencies of 9 -10%. Data collected at the Gudmund-sen Sandhills Laboratory with ges-tating cows grazing winter range sup-port the use of 9-10% microbial effi-ciency for most dormant forages(1993 Nebraska Beef Report, pp. 8-10;1994 Nebraska Beef Report, pp. 5-7;1996 Nebraska Beef Report, pp. 14-16;1997 Nebraska Beef Report, pp. 8-10).With vegetative forages and high-qual-ity hays, we suggest using 13% effi-ciency. Using a too-high microbialefficiency will result in over-predictionof the DIP requirement and overestima-tion of the supply of MP.

Ruminants have the ability to re-cycle nitrogen to the rumen in the formof urea. Therefore, excess MP (or UIP)can likely substitute for DIP. However,excess DIP cannot substitute for MP orUIP. Because of this ability to recyclenitrogen, slight deficiencies in DIP maynot be detrimental to performance, es-pecially when MP supply is greaterthan the requirement.

Table 4 shows the effect of supple-mental rumen degradable protein forgestating spring-calving cows grazingnative winter range on NE

m, DIP and

MP supplies, requirements and balances(1996 Nebraska Beef Report, pp. 14-16). In Year 1, cow weight and condi-tion score changes were similar for alltreatments. In Year 2, cows respondedin a quadratic manner to level of supple-mental DIP. Based on the cow weightchange and condition score data, therumen degradable protein requirementwas not met by the 29% level in Year 2.The NRC model predicted DIP wasslightly deficient at the lowest level ofsupplementation and was adequate forall other treatments in Year 1, indicat-ing only small amounts of supplemen-tal rumen degradable protein are

Table 3. Effect of microbial efficiency on degradable and metabolizable protein requirement,supply and balance for a gestating spring calving cow consuming dormant winter range.

Microbial efficiency

8% 9% 10% 11% 12% 13%

DIP supply (g/d) 436 436 436 436 436 436DIP requirement (g/d) 494 556 618 680 741 803DIP balance (g/d) -58 -120 -182 -244 -305 -367

MP supply (g/d)a 393 432 472 511 551 590MP requirement (g/d) 459 459 459 459 459 459MP balance (g/d) -66 -26 13 52 92 131

aMicrobial MP is calculated in the NRC model from TDN and is not reduced when DIP is less than therequirement.

Table 4. Effect of supplemental rumen degradable protein on DIP and MP supplies, requirementsand balances for gestating spring calving cows grazing native winter range.

Year 1Treatmenta

Item 50% 75% 100% 125%

Daily gain, lb .13 .09 .20 .14Condition score change -.6 -.9 -.8 -.8

NEm supply 15.7 16.9 15.6 16.3NEm requirement 16.4 16.4 16.4 16.4NEm balance -0.7 0.5 -0.8 -0.1

DIP supply 642 760 797 892DIP requirement 663 716 657 689DIP balance -21 44 140 203

MP supply 521 557 505 525MP requirement 455 455 455 455MP balance 66 102 50 70

Year 2Treatmenta

Item 29% 65% 100% 139%

Daily gain, lb .10 .39 .14 .02Condition score change -.2 0 -.4 -.3

NEm supply 13.8 13.9 13.9 13.8NEm requirement 16.6 16.6 16.6 16.6NEm balance -2.8 -2.7 -2.8 -2.8

DIP supply 491 567 648 709DIP requirement 586 589 589 586DIP balance -95 -22 59 123

MP supply 463 460 455 448MP requirement 459 459 459 459MP balance 4 1 -4 -11

aTreatments based on percentage of estimated supplemental degradable intake protein requirement (1996Nebraska Beef Report, pp. 14-16).

a gestating spring-calving cow con-suming dormant winter range. As mi-crobial efficiency changes from 8 to13%, DIP goes from slightly deficientto highly deficient, while MP moves

from deficient to adequate (model doesnot reduce MP if DIP is deficient). Ingeneral, less-digestible forages, whichpass from the rumen at slower rates,have lower microbial efficiencies. For- (Continued on next page)


Table 5. Effect of supplemental ear corn, ear corn plus protein or protein on cow performance,NEm, DIP and MP supplies, requirements and balances for gestating spring calving cowsgrazing native winter range.

Treatmenta

Ear corn +Item Ear corn protein Protein

Cow weight change, lb -121.0b -40.3c 14.6d

NEm supply 15.2 15.3 14.6NEm requirement 16.4 16.4 16.5NEm balance -1.2 -1.1 -1.9

DIP supply 459 569 628DIP requirement 632 634 613DIP balance -173 -65 15

MP supply 543 577 537MP requirement 458 458 458MP balance 85 119 79

aTreatments were 3.5 lbs supplemental ear corn; 3 lbs supplemental ear corn plus 1 lb 40% protein cube;or 2 lbs 32% protein cube (1987 Nebraska Beef Report, pp. 36-37).a,b,c,dMeans in the same row with different superscripts differ, (P<.05).

Table 6. Suggested values for feedstuffs commonly used by Nebraska cattle producers.

eNDF TDN CP DIP

Protein meals

Soybean meal 0 88 49.9 70Sunflower meal 0 65 25.9 81Cottonseed meal 0 75 46.1 57Feather meal 0 88 85.8 30Blood meal 0 88 90.5 25Distillers solubles/steep liquor

(dry milling) 0 88 28 80Distillers solubles/steep liquor

(wet milling) 0 88 36 80

Harvested forages

Corn silage 71 75 7.4 75Alfalfa hay 100 60 16 82Brome hay, mid bloom 100 66 14.4 84Alfalfa hay, early vegetative 100 74 30 93Alfalfa hay, late vegetative 100 67 20.3 85Meadow hay, high quality 100 67 16.2 87Prairie haya 100 49 6.8 80Prairie haya 100 53 7.7 75

Grazed forages

Sandhills range, June diet 100 68 12.4 82Sandhills range, July diet 100 67 10.9 82Sandhills range, August diet 100 64 10.0 84Sandhills range, September diet 100 59 6.6 86Winter native range 100 54 6.2 85

aMatch to nearest CP value.

required to meet the DIP requirement.In Year 2, the NRC model predictedthat cows fed at 29% of the estimatedsupplemental rumen degradable pro-tein requirement were deficient in DIP.In Table 4, the NRC model calculationswere completed using a microbial effi-ciency of 9%. Model predictions wereaccurate when this efficiency value wasused.

Table 5 shows the effect of supple-mental ear corn and/or protein for ges-tating spring-calving cows grazingnative range on cow performance, NE

m,

DIP and MP supplies, requirements andbalances. The NRC model predictedDIP levels were adequate for the pro-tein treatment and deficient for thesupplemental ear corn and ear corn plusprotein treatments. A 9% microbial ef-ficiency was used to calculate the DIPrequirements and MP supplies in Table5. Cow weight gains were highest forthe protein supplemented treatments,intermediate for the ear corn plus pro-tein and lowest for the ear corn treat-ment. Net energy for maintenancebalances were negative for all treat-ments. It is possible the treatments con-taining supplemental ear corn reduceddigestibility and intake of the rangeforage; however, no effort was made tomodel these possibilities as they werenot measured in the trial. If intake anddigestibility were reduced whensupplemental ear corn was fed, NE

m

balances would be more negative forthe treatments containing supplemen-tal ear corn. The NRC model does notreduce energy digestibility when DIP isdeficient. This trial illustrates the im-portance of meeting the DIP require-ment, especially when energy issupplemented.

Table 6 gives suggested values foreffective NDF, CP, DIP and TDN forfeedstuffs commonly used by cow-calfoperations in Nebraska. When actualanalysis values for a particular feedstuffare available, the values from the analy-sis should be used. These suggestedfigures serve only as guidelines.

Table 7 gives guidelines for success-ful use of the NRC Model with grazingcattle. As with any computer program,the output is highly dependent on theinput. Critical areas in the input section

which need attention are: 1) Microbialyield (efficiency); 2) the ‘On Pasture’feature; and 3) the Environment sec-tion. Microbial yield impacts both DIPrequirement and MP supply. We sug-gest using 9 - 10% for low-quality hays,winter range and similar forages. Add

1% for lactating cows. Use 13% forvegetative forages, high-quality haysand other forages > 60% TDN. Forstraws, corn stover and other forages <50% TDN use 8%. The ‘On Pasture’feature will automatically raise energyrequirements by approximately 25% as


Table 7. Suggested inputs and guidelines for use of the 1996 NRC model.

1. Units and Levels Section.Use only Level 1, unless rates of digestion of all feed fractions are known.

2. Animal Section.Remember that your choice of breed affects maintenance energy requirements.Bos indicus cattle have lower NEm requirements, while dairy and dual purpose breeds have higherrequirements. This is discussed in detail in the textbook accompanying the NRC Model.

3. Management Section.A. Using the ‘On Pasture’ feature in the management section will increase maintenance energy

requirements by approximately 25% with level terrain and 50% with hilly terrain. The valuecan be input as a range between 1 (level) and 2 (hilly) in 0.1 unit increments. We recommendusing this feature cautiously. In many cases, maintenance energy requirement is not increasedby 25% while cattle are on pasture. Requirements are calculated accurately for pasture cattleeven if this ‘On Pasture’ feature is turned off.

B. Microbial Yield. Use 13% (default) for all vegetative forages and forages above 60%digestibility. For lower quality forages such as winter range or hays below 55% TDN use amicrobial efficiency of 9-10%. Values as low as 8% may be necessary when the diet consistsof mainly straw, stover, or other forages below 50% TDN which have lower passage rates.After calving, intakes and passage rates increase, therefore, microbial efficiency should beincreased one percentage unit above that of a gestating cow fed the same forage.

4. Environment Section.A. Temperature. Because of daily fluctuations in temperature, it is difficult to state a temperature

which the cattle are subjected to. Interactions also exist with other environmental factors whichare discussed below. We recommend using long term average temperatures for a given monthor season at a given location.

B. Wind speed. Caution is needed when using this feature. Because cattle behavior is impactedby wind speed, cattle are not subjected to reported wind speeds. Wind speed is generallymeasured by anemometers positioned 10' above ground. Cattle are seldom subjected to thesewind speeds because they will find ways to minimize the effect of wind on them. Werecommend using wind speeds of less than 5 miles per hour in most cases.

C. Hair Depth. Use .25 inches in the summer and .5 inches for winter coats.D. Hide. Use 1 (thin hide) for Bos indicus and dairy breed types, and 2 (average) or 3 (thick) for

most English and Continental breeds.

5. Feeds Section.A. Use the Feed Library (a feature separate from the model) to make global changes to feedstuff

composition. Use the Feed Composition feature to make feed composition changes specificto a ration or problem (composition changes made in this manner will be specific to that inputfile only).

B. When estimates of feed intake are unavailable or unknown, use the NRC estimated intake asa guideline. Use the following as general guidelines. Dry gestating cows will generallyconsume 1.8-2.0% of body weight, while lactating cows will consume 2.3-2.5% of bodyweight.

a way of accounting for the energy costof grazing activity. In some cases, whenhilly terrain is an entered factor, theincrease in energy requirement predictedby the model will be as high as 50%. Werecommend cautious use of this feature.Grazing activity does require the ani-mal to expend energy; however theincreases predicted by the model maysometimes be unrealistic. The modelalso is very sensitive to environmentalinputs, particularly wind speed, whenthe animal is below its lower criticaltemperature. We recommend windspeeds of less than 5 mph.

The NRC model is a useful tool forevaluating grazed diets when accurate

estimates of protein degradability, di-gestibility and intake are available.Microbial efficiency appears to be lowerfor less-digestible forages which haveslower rates of passage. The findingthat only small amounts of DIP arenecessary to maintain gestating beefcows indicates that microbial efficiencyis relatively low on these low qualityforages. Microbial efficiency has a largeimpact on estimates of DIP require-ment and consequently MP supply.

1Greg Lardy, former graduate student; DonAdams, Professor, West Central Research andExtension Center, North Platte; Terry Klopfenstein,Dennis Brink, Professors, Animal Science, Lincoln.

Dried PoultryWaste as a

ProteinSupplement forCows GrazingWinter Forages

D. J. JordonTerry Klopfenstein

Don AdamsJackie Johnson

Mark KlemesrudJim Gosey1

Replacing soybean meal withdried poultry waste and feathermeal was effective when supple-menting cows grazing either na-tive Sandhills winter range orcornstalks and saved $55/ton insupplement ingredient costs.

Summary

Two trials conducted in 1996-1997evaluated dried poultry waste relativeto soybean meal for cows grazing win-ter forages. In Trial 1, cows grazingnative Sandhills winter range received:1) no supplement; 2) urea; 3) 22%dried poultry waste+urea; 4) soybeanmeal; 5) 22% dried poultrywaste+soybean meal; or 6) 44% driedpoultry waste. Cows receiving supple-ments gained more weight (P<.001)and maintained greater body condition(P<.001) than unsupplemented cows.Cows receiving urea gained less(P<.10) than cows receiving more natu-ral protein, although body conditionremained similar. In Trial 2, cows graz-ing cornstalks received supplementscontaining either soybean meal or driedpoultry waste; however, gains were notdifferent.



Introduction

Cornstalks and winter range typi-cally are utilized by cow/calf producersin the Midwest and Central Great Plainsas economical alternatives to higher-priced harvested forages. However,grazed winter forages are often defi-cient in degradable intake protein (DIP)and do not meet the metabolizable pro-tein needs of the gestating cow. De-gradable intake protein providesnitrogen to the microbial populationand aids in forage digestion. Generally,supplemental protein is fed to meetthese needs. As a result, protein supple-mentation is often the most costly as-pect of production and an area whichcan be improved. One way to lowersupplement cost is to find alternative,less-expensive protein sources whichadequately meet the cows DIP require-ment. Dried poultry waste (DPW) is anacceptable source of DIP for calves ona growing ration; however, DPW hasnot been evaluated as a source of DIPfor cows grazing low-quality forages.Dried poultry waste is approximately28% protein and 35% ash. Of the 28%protein, 49% is true protein; the re-mainder is uric acid. In addition, DPWbrings minerals such as calcium, phos-phorus, copper and zinc to the supple-ment, further reducing supplement costs.

Two trials were conducted to evalu-ate dried poultry waste relative to soy-bean meal (SBM) as a degradable intakeprotein source for cows on low-qualityforages.

Procedure

Trial 1

To evaluate DPW as a DIP source,60 cows (5 yr, 1,223 lb) grazing nativeSandhills winter range were used in a108-d individual supplementation trialbeginning November 19, 1996 and end-ing March 4, 1997. Cows were assignedrandomly to one of six supplementaltreatments (10 hd/treatment). Treat-ments (Table 1) consisted of: 1) Nosupplementation; 2) Urea; 3) 22% DPW+ Urea; 4) SBM; 5) 22% DPW + SBM;and 6) 44% DPW. In addition, feathermeal was added in varying amounts to

each supplement in order to supplyadequate undegradable intake protein(UIP) to the cows and to equalize UIPcontent. Supplements were formulatedto be equal in terms of both DIP and UIPand fed in a cube form (7/8"). Cowswere offered 2 lb (as-is) on Monday andWednesday and 3 lb on Friday. Cowswere gathered from a common pasture,sorted in a temporary corral, placed intoan individual pen and fed the assignedsupplement. Cows were given severalminutes to consume their supplement;however, most were finished within 5minutes. Cows on the control treatmentwere sorted in the corral and turnedback into the pasture. All cows wereallowed ad-libitum access to salt andlimestone.

Forage intake was determined fromthe fecal output and forage indigestibil-ity of 36 cows (6 cows/treatment) overa five-day collection period (December16, 1996 through December 20, 1996).Five days prior to the start of collection,cows on the intake portion of the trialwere dosed with an intraruminal con-tinuous chromium-releasing bolus todetermine fecal output.

Five, 550 lb steers were fitted withfecal collection bags for a total fecalcollection and dosed with the sameintraruminal continuous chromium-re-leasing boluses as the cows to deter-

mine a correction factor for chromiumpayout.

Diet samples were collected fromsix esophageally-fistulated cows (1,250lb) on one day during the intake period.Although a second diet collection wasplanned, inclement weather would notpermit it. Diet samples were freezedried, ground and analyzed to deter-mine CP, UIP and digestibility. Forageintake was determined by dividing fe-cal output by indigestibility of the rangediet collected by the esophageallyfistulated cows.

Initial and final weights were deter-mined by taking the average of twoconsecutive day weights at the begin-ning and end of the trial. A one daymidpoint weight also was collected.Body condition scores (1 = thinnest to 9= fattest) also were determined by pal-pation of the ribs and thoracic vertebraeat the beginning, middle and end of thetrial.

Trial 2

A completely randomized designusing 48 cows (6 yr, 1,300 lb) evaluateda supplement containing DPW versus asupplement containing SBM for cowsgrazing winter corn residue from No-vember 5, 1996 through January 8, 1997.Treatments were: 1) SBM; and 2) 44%

Table 1. Supplement composition for Trials 1 and 2.

Supplement (% of DM)a

22% DPW 22% DPWIngredient Ureab + Ureab SBMb,c + SBMb DPWb,c

Wheat midds 27.1 18.4 8.26 9.19 8.22Soybean hulls 27.1 18.4 8.26 9.19 8.22Feather meal 23.6 24.8 11.5 18.8 26.3Dried poultry waste —— 22.0 —— 22.0 44.0Urea 3.44 1.7 —— —— ——Soybean meal—47% —— —— 54.5 26.9 ——Molasses 4.0 4.0 4.0 4.0 4.0Tallow 2.0 2.0 2.0 2.0 2.0Salt 2.64 2.30 2.88 2.41 1.94Dicalcium phosphate 2.5 0.42 2.06 0.21 ——Potassium chloride 1.3 0.61 —— —— ——Copper sulfate 0.08 0.056 0.036 0.034 0.033Limestone 1.0 —— 1.16 —— ——Zinc sulfate —— —— 0.044 0.021 ——Vitamin A, D, E 0.25 0.25 0.25 0.25 0.25Ameribond 5.0 5.0 5.0 5.0 5.0

aDPW=dried poultry waste; SBM = soybean meal.bTrial 1 supplements.cTrial 2 supplements.


DPW. Supplements were the same astreatments 4 (SBM) and 5 (44% DPW)in Trial 1 (Table 1). Cows were as-signed randomly to one of six irrigatedcorn fields (3 cornfields/treatment) at astocking rate of 0.8 hd/acre. Supple-ments were fed once daily at 1.25 lb (as-is) in a cube form (7/8").

Animal performance was measuredin terms of ADG. Both initial and finalweights were the average of two con-secutive day weights following threedays of limit feeding at 2% of bodyweight. Cows were removed from fieldswhen, based on visual appraisal, quan-tity of forage became limiting.

Results

Trial 1

Cows consuming supplement gainedmore weight (Table 2) and maintainedmore body condition (P<.001) thanunsupplemented cows. Each treatmententered the trial with BCS ranging from5.0-5.2. By the end of the trial, supple-mented cow BCS averaged 4.3, whileunsupplemented cows had an averageBCS of 3.9. Average daily gain andBCS results indicate the control cowswere deficient in DIP. Other work sup-ports this conclusion and has shownnative Sandhills winter range is defi-cient in supplying cows with DIP andthat cows may respond positively toDIP supplementation (1996 NebraskaBeef Cattle Report, pp. 14-16). How-ever, because supplemented cows didreceive energy and added minerals fromthe supplements, at least some of thisresponse may have been due to energyor any one of the supplemented miner-

als such as Cu, Zn or P.Overall, cows consuming natural

protein supplements performed better(P<.10) than cows fed urea, indicatingprotein may be required either by theanimal or the microbial population(Table 2). Natural protein may beimportant as a source of amino acidsto be utilized by the microbial popula-tion. Protein also may have a slowerrate of nitrogen release which moreclosely corresponds to energy releasefrom the slowly digested winter forage.By feeding on alternate days, urea,which is highly soluble in the rumen,would have been immediately avail-able to the microbial population. Dueto the slow rate of forage digestion,however, energy would be limiting tomicrobial protein production, makingthe microorganisms dependent uponnitrogen recycling by the animal asenergy became available. Body condi-tion scores of cows supplemented withurea were similar to those of cowssupplemented with natural protein.

Compared to SBM, cows consum-ing supplements containing DPW hadsimilar weight gains (Table 2) and BCSthroughout the trial. No differences werefound in ADG (Table 2) or BCS through-out the trial for cows consuming 44%DPW, 22% DPW + urea or 22% DPW+ SBM.

Cows consuming either 22% DPW +urea or 22% DPW + SBM had similarADG (Table 2) and equal BCS. There-fore, if natural protein was required bythe microbial population, the DPW andfeather meal were supplying adequateamounts.

Esophageally fistulated cows wereable to consume diets containing 6.84%

CP (DM basis), of which 0.55% wasUIP (DM basis). In vitro organic mat-ter disappearance (IVOMD) of dietscollected by esophageal cows was48.5% (DM basis), slightly belowIVOMD values typically seen (50-52%)on native Sandhills winter range. How-ever, diet collections for this trial weretaken one day after four consecutivesub-zero days. Cows may have experi-enced limited grazing time in the daysprevious to collections, were hungry,and therefore less selective.

No differences were found in forageorganic matter intake (lb; Table 3) ortotal organic matter intake (lb; Table 3)throughout the trial.

Trial 2

No differences in ADG betweenDPW and SBM were observed. Perfor-mance of cows consuming SBM orDPW were -0.61 and -0.62, respec-tively. The fact that cows lost weightwould indicate the corn residue was ofa poorer quality than in previous years.

A major factor determining residuequality is the amount of corn grainremaining in the field after harvest.Initially, corn grain supplies a substan-tial amount of protein and energy to thecows and accounts for a significantportion of gain. Based on samples col-lected for other cornstalk grazing trialsin 1996-97, little residual corn was avail-able in fields.

Protein studies, especially thoseusing cornstalk grazing, can be con-founded by corn intake. The fact thatcows are consuming ad-libitum quan-tities of corn residue and the variable


Table 2. Weight gains of cows grazing native Sandhills winter range (Trial 1).

Treatmenta Contrastsb (P =)

Itema Control Urea DPW + Urea SBM DPW + SBM DPW A B C D E

IWT, lb 1226 1219 1225 1204 1223 1219 NS NS NS NS NSMWT, lb 1179 1195 1197 1181 1187 1192 NS NS NS NS NSFWT, lb 1169 1217 1247 1216 1243 1242 0.08 NS NS NS NSADG, lb/d

days 0-53 -0.89 -0.44 -0.53 -0.43 -0.68 -0.51 0.07 NS NS NS NSdays 53-106 -0.19 0.41 0.95 0.65 1.05 0.95 <0.001 0.006 0.09 NS NSdays 0-106 -0.54 -0.02 0.21 0.11 0.18 0.22 <0.001 0.10 NS NS NS

aDPW = dried poultry waste; SBM = soybean meal; IWT = initial weight; MWT = mid-point weight; FWT = final weight.bContrasts were A (control vs. urea, DPW + urea, SBM, DPW + SBM, DPW), B (urea vs. DPW + urea, SBM, DPW + SBM, DPW), C (SBM vs. DPW + Urea,DPW + SBM, DPW), D (DPW vs. DPW + urea, DPW + SBM), E (DPW + urea vs. DPW + SBM); NS = nonsignificant.


Table 3. Cow daily forage and total organic matter intake (Trial 1).

Treatmenta Contrastsb (P =)

Itema Control Urea DPW + Urea SBM DPW + SBM DPW A B C D E

FOMI (lb) 29.9 29.6 27.8 29.2 27.3 28.1 NS NS NS NS NSTOMI (lb) 29.9 30.4 28.6 30.0 28.1 28.9 NS NS NS NS NS

aDPW = dried poultry waste; SBM = soybean meal; FOMI = forage organic matter intake; TOMI = total organic matter intake.bContrasts were A (control vs. urea, DPW + urea, SBM, DPW + SBM, DPW), B (urea vs. DPW + urea, SBM, DPW + SBM, DPW), C (SBM vs. DPW + Urea,DPW + SBM, DPW), D (DPW vs. DPW + urea, DPW + SBM), E (DPW + urea vs. DPW + SBM); NS = nonsignificant.

amount of downed corn often do notallow for the control of corn intake byanimals in trials such as these.

Another likely factor for the ob-served weight loss was inclementweather. When energy requirementsbecome greater than can be met byavailable forage, animals mobilize bodyreserves for heat production. Althoughthe weather was favorable during mostof the trial, a relatively severe coldperiod did occur during the last twoweeks of the trial. This cold period alsocorresponded to the time of most lim-ited forage.

Based on visual observationsthroughout both Trials 1 and 2, DPW isas acceptable to cows as SBM. In bothtrials, with the exception of a singleanimal on the DPW treatment in each,the cows readily consumed all supple-ments. Cows in both Trials 1 and 2came to the supplements and quicklyconsumed all cubes from day 1 throughthe end of the trials.

For cows on winter range or cowsconsuming corn residues, dried poultrywaste and feather meal appear to beviable substitutes compared to moretraditional protein supplement ingredi-

ents such as soybean meal. Economicanalysis of the DPW and SBM supple-ments used in the present trials indicatethe DPW supplement was $57 less/ton,resulting in a savings of $0.04/hd/dayand a total savings over 80 days of$3.20/hd.

1D. J. Jordon, graduate student; TerryKlopfenstein, Professor, Animal Science, Lincoln;Don Adams, Professor; Jackie Johnson, researchtechnician, West Central Research and ExtensionCenter, North Platte; Mark Klemesrud, researchtechnician, Animal Science, Lincoln; Jim Gosey,Professor, Animal Science, Lincoln.

Escape Protein Supplementation and WeaningEffects on Calves Grazing Meadow Regrowth

Greg LardyDon Adams

Terry KlopfensteinJune Ueckert

Richard Clark 1

High-quality meadow regrowthis limiting in escape protein. Milkis an important source of metabo-lizable protein however, milk in-take in late lactation may not besufficient to maximize growth ofnursing calves.

Summary

Forty spring-born calves grazingsubirrigated meadow regrowth wereassigned to two weaning and twosupplementation treatments in the fallof 1995 and 1996. Weaning treatmentswere: 1) weaning September 1; or 2)

bypasses rumen fermentation by theesophageal groove reflex and is di-gested and absorbed in the abomasumand small intestine. Because of thisreflex, milk protein represents an im-portant contribution to the metaboliz-able protein supply for the nursing calf.Nursing calves have higher relativeprotein requirements than more matureanimals.

Generally, when cattle graze cool-season grasses, ruminal ammonia con-centrations do not limit microbialgrowth and fermentation. However,because of the degradable nature of theprotein in these grasses, large amountsof nitrogen can be lost as ammoniabefore reaching the duodenum. There-fore, it is possible for metabolizableprotein to be limiting in forages whichhave relatively high crude protein con-tents, especially if relative requirementsare high.

Numerous studies have evaluated

nursing during the trial. Supplemen-tation treatments were 1) no supple-mental undegraded intake protein(escape protein); or 2) supplementalundegraded intake protein. Notreatment interactions were detectedindicating weaning and supplemen-tation affects were independent.Nursing calves had higher weightgains (2.1 versus 1.3 lb/day) andlower forage intakes (5.2 versus 6.5lb/day) than weaned calves. Sup-plemental undegraded intake pro-tein increased weight gains of calves(1.94 versus 1.45 lb/day). We con-cluded subirrigated meadow foragewas limiting in metabolizable proteinand milk was an important sourceof metabolizable protein.

Introduction

For the nursing calf, milk representsan important source of nutrients. Milk


the effects of early weaning on cow andcalf performance. However, these stud-ies generally involved feeding earlyweaned calves large amounts of con-centrates or grains, rather than leavingcalves in a grazing setting. Few studieshave evaluated the effect of early wean-ing on calf performance, where calvesgraze high-quality forages after wean-ing. Effects of supplemental, unde-graded intake protein on forage intakeand performance of the weaned andnursing calves grazing high-quality for-age are not well-defined. Supplyingundegraded intake protein in the formof milk or in a supplement may increaseperformance of calves grazing meadowregrowth if metabolizable protein isdeficient in those forages. Our objec-tives were to evaluate the effects ofmilk intake and supplemental unde-graded intake protein on calf perfor-mance and forage intake while grazingsubirrigated meadow regrowth in theNebraska Sandhills.

Procedure

The study was conducted at the Uni-versity of Nebraska-Lincoln Gud-mundsen Sandhills Laboratory. Fortyspring-born crossbred calves were as-signed in each year to two weaning andtwo supplementation treatments duringthe fall of 1995 and of 1996. Becausethe calves did not readily consumesupplements until mid-October, 1995,the trial lasted from October 17 to No-vember 18. In 1996, however, the calvesreadily consumed supplements from theoutset and the trial lasted from Septem-ber 5 to November 4. Each year, calvesgrazed subirrigated meadow regrowthafter July haying. Weaning treatmentswere: 1) weaning before the trial began(September 1); and 2) nursing through-out the trial. Supplementation treat-ments were: 1) no supplementation; or2) supplemental undegraded intake pro-tein. Supplement composition is listedin Table 1. Weaned calves receivingsupplement were individually fed 2.0 lbof supplement daily; nursing calves re-ceived 1.1 lb supplement daily.

Calves were gathered each day at7:30 a.m. and individually fed theirsupplements. In order to prevent nurs-

ing by weaned calves, the subirrigatedmeadow pasture was split in 1995 intotwo pastures; nursing calves grazed onone side, and weaned calves on theother. Each day, following supplemen-tation, nursing and weaned calves ro-tated pastures. Over the course of thetrial, each group of calves grazed eachside a similar number of days. In 1996,nursing and weaned calves were pas-tured together and observed for crossnursing. No nursing by weaned calveswas observed in either year. Milk in-take by nursing calves was determinedby weigh-suckle-weigh on November4, 1995 and October 18, 1996.

Fecal output was determined on steercalves during October of each year.Each steer calf was dosed with a chro-mium-releasing Captec bolus. Fecaloutput was calculated by dividing theamount of chromium released by theCaptec bolus by the chromium concen-tration in the feces. Forage intake wascalculated by dividing fecal output byindigestibility of the subirrigatedmeadow diet.

Forage diet samples were collectedwith three esophageally fistulated cowsand three ruminally fistulated nursing

calves. Extrusa samples were analyzedfor DM, OM, CP, NDF, ADF, IVOMDand protein degradability

Results

Year effects were significant for ini-tial weight and average daily gain (P =0.06 and 0.04, respectively). Initialweights averaged 478.3 and 423.9 lb in1995 and 1996, respectively. Theseweights were higher in 1995 because ofthe difficulties in getting calves to con-sume supplements, which caused thetrial to start later than anticipated. Av-erage daily gains averaged 1.52 and1.87 lb day-1 in 1995 and 1996, respec-tively, and again were likely influencedby the starting date of the trial.

Calves and cows selected diets whichwere similar in quality. Diets collectedwith ruminally cannulated calves aver-aged 12.5% CP and 54.8% IVOMD(Table 2). While grazing meadow re-growth, calves tended to select dietshigher in undegraded intake proteinthan cows (Table 2).

No supplementation by weaningmanagement interactions were detectedfor initial weight, final weight or aver-age daily gain. No supplementation byweaning management interactions weredetected for forage intake, total intake,forage intake as a percentage of bodyweight or total intake as a percentage ofbody weight. Therefore only maineffects will be presented and discussed.

Nursing calves had higher averagedaily gains and higher final weights(P < .01) compared to weaned calves(Table 3). Due to the magnitude of thisresponse, it is apparent that milk was animportant source of nutrients for thegrowing calf. Nursing calves gained

Table 1. Composition of supplement fed toweaned and nursing calves (drymatter basis).

Ingredient % of DM

Sulfite liquor treatedsoybean meal 80.0

Feather meal 20.0

% of OM

Crude protein 57.3In vitro organic matter

disappearance 79.5Undegraded intake protein,

% crude proteina 78.8

aDetermined using ammonia release procedure.


Table 2. Crude protein (CP), undegraded intake protein (UIP), neutral detergent fiber (NDF), aciddetergent fiber (ADF) and in vitro organic matter digestibility (IVOMD) of diet samplescollected from cows and calves grazing subirrigated meadow regrowth in 1995 and 1996.

% of organic matter

Date Type CP UIP NDF ADF IVOMD

27 Oct., 1995 Cow 10.0 1.94 84.4 57.2 53.127 Oct., 1995 Calf 10.9 2.45 83.9 55.9 50.1 3 Nov., 1995 Calf 11.5 2.21 76.3 53.0 56.115 Oct., 1996 Cow 11.1 1.78 76.5 53.2 55.715 Oct., 1996 Calf 11.2 2.72 88.8 63.0 56.716 Oct., 1996 Calf 16.2 3.09 94.4 69.8 56.3


0.79 lb/day more than weaned calvesover a 60 day grazing period, resultingin over 44 lb of body weight gain percalf. Lactation effects on weight andbody condition score changes in thecow were not investigated. Previousresearch at Gudmundsen SandhillsLaboratory indicated lactating two-year-old cows will maintain weight and bodycondition while grazing meadow re-growth (1996 Nebraska Beef Report,pp. 3-5), however body condition in-creased when cows were dry.

Calves receiving undegraded intakeprotein supplementation had higher (P= 0.03) weight gains compared to non-supplemented calves (Table 3). Weanedand nursing calves responded to supple-mental undegraded intake protein in asimilar fashion, indicating theundegraded intake protein was likelyfirst limiting for both weaned and nurs-ing calves.

Forage intake and total intake, whenexpressed either as a percentage of body

Table 3. Effect of weaning and supplementation on ADG and intake.

Main effectsa

Weaning management Supplementation

Non- Supple-Weaned Nursing P-value supplemented mented P value

Initial weight (lb) 432 470 .2072 457 446 .7560Final weight (lb) 490 569 .0099 524 535 .6847ADG (lb/day) 1.3 2.1 .0009 1.5 1.9 .0306Forage intake (lb/day) 6.5 5.2 .0090 6.0 5.7 .3257Total intake (forage +

supplement, lb/day) 7.50 5.74 .0040 6.00 7.26 .0111Forage intake

(% body weight) 1.29 0.89 .0074 1.17 1.02 .0927Total intake

(forage + supplement,% body weight) 1.48 0.99 .0048 1.17 1.30 .1388

aAll supplement by weaning management interactions were nonsignificant at P>0.15.

weight or as an amount, were higher(P<.01) for weaned compared to nurs-ing steers (Table 4). Although weanedcalves compensated for lack of milkintake by increasing forage intake, thiscompensation was not enough to in-crease weight gains to levels of nursingcalves, indicating the importance ofmilk for the growing calf.

No differences were found in forageintake for supplemented or non-supple-mented steers. Intake of forage andsupplement were higher (P < .01) forsupplemented steers. Forage intake, asa percentage of body weight, tended tobe higher for nonsupplemented steers(P=.09). Total intake, expressed as apercentage of body weight, tended to behigher for supplemented calves(P=0.14).

Milk consumption averaged 12.8 and14.5 lb milk/day for supplemented andnonsupplemented calves, respectively.Assuming milk contains 3.4% protein,these milk intakes would supply 0.43

and .46 lb metabolizable protein,respectively. For the nursing calvesnot receiving the undegraded intakeprotein supplement, this representsover 50% of the metabolizable proteinsupply. However, based on the supple-mentation performance responses,milk may not supply adequate metabo-lizable protein to meet the require-ments for the level of daily gain bythe calves that other nutrients in thegrazed forage would support.

Commonly accepted practices ofcreep feeding cereal grains to nursingcalves may not correct metabolizableprotein deficiencies in high qualityforages. Creep feeding small amountsof protein supplements high inundegraded intake protein may increaseweight gains in nursing and weanedcalves grazing high-quality forages.

We concluded that high-quality for-ages, such as subirrigated meadowregrowth, may be limiting in metab-olizable protein for growing calves.Even though milk represents an impor-tant source of metabolizable protein,milk intake in late lactation may not behigh enough to support the level ofgrowth that would be supported by theenergy consumed.

1Greg Lardy, former research associate, AnimalScience, Lincoln; Don Adams, Professor, AnimalScience, West Central Research and ExtensionCenter, North Platte; Terry Klopfenstein, Professor,Animal Science, Lincoln; June Ueckert, researchtechnician, Gudmundsen Sandhills Laboratory,Whitman; Richard Clark, Professor, AgriculturalEconomics, West Central Research and ExtensionCenter, North Platte.


Table 1. ARD calving score assigned to each parturition.

Calving Score Assignment Criteria

1. Unassisted delivery.

2. Little difficulty. Assistance given by hand, but no calfjack or puller used.Assistance may not have been required.

3. Moderate difficulty. Calfjack was used, typically pull duration was less than10 minutes.

4. Major difficulty. Calfjack used and major difficulty encountered. Duration ofpull longer than 10 minutes.

5. A cesarean section was preformed.

Calving Difficulty and Calf Response to Stress


Todd CappelAndrea BuenoEdd Clemens1

Calving difficulty of the heifercan significantly depress some ofher calf’s physiological resourcesused to adjust to the stress of theirnew environment.

Summary

Calving difficulty altered the stress-related capabilities of the calf, placingthe newborn in a compromised situa-tion. Calves derived by severe mechani-cal pull or cesarean section exhibiteddepressed short-term defensive capa-bilities, lower cortisol and elevatedneutrophil values, necessary for fight-ing infectious organisms. Of equal con-cern: when compared to calves bornwith little or no parturition difficulty,the stressed calves failed to developeffective adaptive mechanisms, havinglower thyroid activity and lymphocytevalues of principle importance for long-term survival. Neither the heifer’s moth-ering ability nor her disposition tendedto influence her calf’s stress indica-tors.

Introduction

Parturition can be stressful for boththe first calf heifer and her calf. Severalphysiological changes occur respond-ing to the stress of parturition in aneffort to maintain normal body func-tion. For example, fetal cortisol is

thought to be one of the primary changesin the calf’s blood that initiate parturi-tion in cattle. With respect to ther-moregulation, T

3 has pronounced effects

on brown adipose tissue utilization andsubsequently the thermogenesis of thenewborn.

Calf mortality represents a economicloss to the beef industry. Studies sug-gest the number of calves lost fromcalving difficulty (50.9%) exceededlosses from all other causes. Calf deathdue to calving difficulty also accountedfor the single largest loss categorythrough the first 96 hours of life. There-fore, calving difficulty, and the endo-crine response to stress represents amajor part of all economic loss in thecow herd. This study was designed toevaluate the relationship between theseverity of calving difficulty and thehormone concentration and blood com-position of the heifer and her calf.

Procedure

A total of 104 first-calf heifers wereused in the experiment, over a two-yearperiod. The heifers were from four uni-

versity herds. The first two groups in-cluded; 36 MARC-MARC III and 10purebred Angus first-calf heifers fromthe Agriculture Research and Develop-ment Center (ARD) near Mead, Ne-braska. For these, the calving seasonbegan February 17 and ended March12, 1995. During the second-year calv-ing season, February 24 to April 4,1996, 18 MARC II first-calf heifersfrom the West Central Research andExtension Center at North Platte, and40 3/4 Angus X 1/4 Gelbvieh heifersfrom the ARD Center near Mead, Ne-braska were sampled.

Pregnant heifers, kept in a calvingpasture with free access to water andalfalfa hay, were checked at one hourintervals for oncoming signs of parturi-tion. After exhibiting stage II labor forone hour (i.e. rupture of the fetal sac,fluid escape from the vulva and ab-dominal strain) the heifer was broughtinto the calving barn. An experiencedherdsman assisted each heifer at partu-rition and assessed the level of calvingdifficulty (Table 1).


Immediately following birth, bloodsamples were obtained from the heiferand calf via jugular venipuncture. Calveswere then bled in the same manner at24, 48 and 72 hours of age. Dates,calving time and blood sampling wererecorded. The dam’s disposition andmothering ability were also assessedand the climatic conditions at the timeof birth recorded. After ensuring properpostpartum care, heifer-calf pairs wereplaced in individual stalls for 24 hours,with fresh straw, feed and water. Uponcompletion of the 24 hour sampling ofthe calf, the pair was released into apost-calving pasture. The last twosamples from the calves were taken inthe pasture.

Blood samples were prepared andanalyzed for; pack cell volume (PCV),differential white blood cell count(WBC), plasma cortisol and plasmatriiodotyrosine (T

3). Statistical differ-

ences were determined by SAS analy-sis. All values are reported as means.

Results

Significant differences were not de-tected (P>.05) for breed of cattle or yearof sampling. Thus, all heifer-calf pairswere grouped together for the statisticalanalysis.

Plasma cortisol concentrations, with-in birthing heifers, were significantlygreater (P<.03) for those animals requir-ing severe mechanical pull or cesareansection, relative to heifers needing noassistance in the delivery of their calf(Figure 1). Statistical differences werealso noted for heifers requiring modestmechanical assistance (less than 10minutes) and those undergoing C-sec-tion (P<.05). It is important to note C-sections were preformed after failure todeliver the calf with mechanical assis-tance. Clearly those heifers requiringextensive mechanical assistance and/orsurgical intervention were undergoingan acute stress, as is evident from theelevated cortisol values. Cortisol con-centrations were not statistically differ-ent for heifers delivering bull versusheifer calves (Figure 1).

Cortisol, the stress indicator so iden-tifiable in the heifer and clearly associ-ated with the degree of calving difficulty,

Figure 1. Concentration of cortisol in heifers at parturition as effected by the degree of calvingdifficulty and by calf sex. (P<.03; 1 vs. 4 & 5. P<.05; 2,3 vs. 5).

Figure 2. Concentration of cortisol in calves at birth and at 24, 48 and 72 hours of age as effectedby the degree of calving difficulty. (Birth; P<.08; 1,2,3 vs. 4. 72 hrs; P<.07; 1 vs. 4,5).

was also in high concentrations withinthe calf population at the time of partu-rition (Figure 2). Cortisol values for thecalf at parturition were higher (P<.08)in those calves delivered using moreadverse procedures (i.e. severe mechani-cal pull versus hand or modest me-chanical pull). It is important to notethat high levels of cortisol are a favor-able endocrine response for the new-born calf, considering the multiple rollscortisol plays in the early survival ofthat calf. While cortisol’s stress defensemechanisms are short-lived, and fall off

rapidly within the first 24 hours of life(Figure 2), it does appear to maintain aslightly elevated concentration in thosecalves from difficult births. Calves re-quiring little or no assistance at birthmaintained a reasonably constantplasma cortisol concentration duringthe three days following parturition.Calves requiring mechanical or surgi-cal intervention, however, experienceda continual decline in cortisol valuessuch that they were considerably lessthan unassisted calves at 72 hours post-partum (P<.07). The lower cortisol val-

0.25

0.2

0.15

0.1

0.05

0

ug

/ul

1 2 3 4 5 Hfr Bull

Calving Score

123123123123123123123

123123123123123123123123

123123123123123123123123123

123123123123123123123

121212121212

0.6

0.5

0.4

0.3

0.2

0.1

0

ng

/ml

1 2 3 4 5

Calving Score

Birth 24 hr 48 hr 72 hr123123


Table 2. Neutrophil:lymphocyte ratio for calves at the time of birth, and at 24, 48 and 72 hourspostpartum.

Calving ScoreHoursPostpartum 1 2 3 4 5

Birtha 2.39 1.26 1.77 2.34 1.5924 hrs 1.98 1.49 2.20 1.81 1.0448 hrs 0.99 1.10 0.91 1.07 0.4472 hrsb 1.48 0.79 1.38 1.82 2.08

aP<.05, 1 vs. 2.bP<.08 1,2,3 vs. 4 and 5

Figure 3. Concentration on T3 in calves at birth and at 24, 48 and 72 hours of age as effected by thedegree of calving difficulty. (Birth; P<.05, 1,2,3,4 vs. 5. 24 hrs; P<.02, 1,2,3 vs. 4,5. 48 hrs;P<.06, 1,2,3 vs. 4. 72 hrs; P<.08, 1,2 vs. 5).

ues are of concern, if, in fact, those firstthree to four days of life are the criticaltime in a calf’s survival.

The calf’s long-term survival skillsmight better be viewed via the study ofplasma triiodotyrosine (T

3) during neo-

natal life. T3 sets the metabolic state of

the animal, responding to both externaland internal stress factors (e.g. climaticchanges, body size, brown fat thermo-genesis and muscular, circulatory andrespiratory activities of the body). Therewere no differences in T

3 among calv-

ing scores at the time of parturition(Figure 3), and presumably no differ-ence in the metabolic state of calvesderived with or without mechanical in-tervention. The exception to this was

the cesarian born calves (P<.05). Physi-ologically, within the first 24 hours T

3

values should be increasing. However,calves born via severe mechanical pullor C-section exhibited a marked reduc-tion in circulating thyroid hormone(P<.02), relative to unassisted deliveryor modest assistance. The depressed T

3

is concerning when considering theJanuary/February calving dates, theharsh environmental temperatures dur-ing this period and the critical need forbody heat and muscular activity of thenewborn calf.

Furthermore, knowledge of T3 activ-

ity indicates the thyroid gland takesseveral days to respond to environmen-tal stress. And T

3, unlike cortisol, is a

long-term stress “adaptation mecha-nism”, rather than an immediate de-fense response. Because of this, it isexpected that on the third or fourth dayof life, T

3 levels should be high. Once

again, as with the cortisol values, calvesdelivered via severe mechanical pull orC-section exhibited a depressed endo-crine response in association with thestress of parturition (Figure 3).

Like cortisol and T3, the neutro-

phil:lymphocyte ratio (N:L) derivedfrom the WBC count has been usedextensively as an indicator of stress andmorbidity. Neutrophils (phagocyticcells) increase in numbers during anacute stress, are short-lived and areconsidered stress defense cells. Con-versely, lymphocytes (immune responsecells) respond more slowly, exist incirculation longer, and are consideredstress adaptation cells. While statisticaldifferences were generally not notedduring the early periods (Table 2), at 72hours postpartum the N:L ratio wassignificantly higher (P<.08) for thosecalves derived via severe mechanicalpull or C-section, relative to the unas-sisted or modest assistance calves. Aswith cortisol and T

3, the high N:L ratio

clearly suggests calves of difficult birthare exhibiting a stress defense response(high neutrophils) and have yet to adaptto their new environment (low lympho-cyte).

The significance of this researchindicates the degree of calving diffi-culty has a pronounced effect upon thatcalf’s ability to adapt to its new envi-ronment. Those calves requiring exten-sive mechanical assistance and/orsurgical intervention express depressedcortisol and neutrophil values neces-sary for the immediate adjustment totheir new environment. Their survivalskills are further compromised viadepressed metabolic adaptation capa-bilities (i.e. reduced T

3 and low lym-

phocyte concentrations) essential forthat calf’s first few days of life.

1Todd Cappel and Andrea Bueno, graduatestudents, Edd Clemens, Professor of Animals Science,Lincoln.

5000

4000

3000

2000

1000

0

ug

/ul

1 2 3 4 5

Calving Score

Birth 24 hr 48 hr 72 hr


Effect of Summer Grazing on Crude Protein andDigestibility of Winter Diets of Cattle in the

Nebraska SandhillsWinter diets of cattle on Sandhills

range are usually less than 6% CP. Dueto this low quality relative to cattleneeds, winter grazing is normallycoupled with protein supplementation.Lack of data describing winter dietquality variability and factors relatingit to present difficulty in balancingsupplementation needs with basalrange diet quality. Since both over- andunder-feeding of supplement can becostly, it is important to characterizewinter diet quality as affected by sum-mer grazing management.

The objective of this research was todetermine the effects of June or Julygrazing at four levels of forage removalon the chemical composition and di-gestibility of sandhills winter range di-ets.

Procedure

In this study, 21 upland native rangepastures, 2.47 acres each, were used atGudmundsen Sandhills Laboratory.During the growing seasons of 1995and 1996, seven grazing treatments wereapplied to these pastures (three pas-tures/treatment). Treatments consistedof a control with no summer grazingand June or July grazing at three stock-ing rates each. Stocking rates were 33,67 and 100% of the stocking rate (.6

AUM’s/acre) recommended for theupland range site where the study pas-tures are located.

Following summer grazing, pastureswere winter diet sampled using twoesophageally fistulated cows per pas-ture. Diet samples were obtained afterallowing cows to graze each pasture for45 minutes. Sampling dates for bothstudy years were early November, earlyJanuary and late March. After dietsamples were freeze-dried and ground,the two samples obtained from eachpasture were composited on an equalweight basis. Composited samples werethen analyzed for CP and IVDMD.

Results

Table 1 shows the CP levels anddigestibility of November, January andMarch diets from the two years of thestudy. There was a year “x” samplingdate interaction (P < .005) which isreflective of different CP changes oversampling dates in year 1 relative to year2. Lower CP in January diets comparedto other sampling dates in year 1 mayhave been due to snow cover affectingthe cows’ ability to select a higher-quality diet. There was also snow coveroffering a possible explanation for thelower observed CP in both January andMarch of year 2. Digestibility of winter

Dale DownsDon Adams

Terry KlopfensteinWalt SchachtPatrick Reece1

Year and winter sampling datesignificantly affect quality of win-ter diet samples from sandhillsrange, whereas summer stockingrate and date of summer grazing donot have a large impact.

Summary

Twenty-one pastures (three pastures/treatment) were used in a two-yearstudy to determine the effects of sum-mer grazing on winter diet quality ofSandhills range. Summer grazing treat-ments consisted of no summer grazing(control) and June or July grazing atthree stocking rates. After summergrazing, pastures were then diet sam-pled using esophageally fistulatedcows in November, January and Marchfollowing summer treatments. Year andsampling date had a significant effecton CP and IVDMD of winter rangediets, whereas summer grazing treat-ments did not have a large impact.

Introduction

Rotational grazing is a prevalentrange management practice in the Ne-braska Sandhills. Many ranches em-ploying rotational grazing graze pasturesone or more times during the spring andsummer and graze residual/regrowthforage in the winter. The nutritionalvalue of winter forage is variable, notwell-defined and may vary with dateand/or amount grazed during the grow-ing season.

Table 1. Crude protein content and digestibility by year and month of winter diet samples fromsandhills range, DM basis.

Winter 1995-96 Winter 1996-97

Sampling date

Item Nov Jan Mar Nov Jan Mar

CPa 6.5 6.0 7.0 5.5 4.7 4.2IVDMD b 55.9 55.1 55.0 52.7 52.2 53.3

aYear x sampling date interaction (P < .005).bYear main effect (P < .05).


year-of-winter sampling caused varia-tion in CP and digestibility and month-of-winter sampling affected CP of winterdiet samples. Small differences inchemical composition, especially CP,could have a notable effect on supple-mentation and cow performance over awinter grazing season. The variation inCP and IVDMD observed in this studyis evidence that winter diet quality isnot static and is an important manage-ment consideration.

1Dale Downs, graduate student; Don Adams,Professor, Animal Science, West Central Researchand Extension Center, North Platte; TerryKlopfenstein, Professor, Animal Science, Lincoln;Walt Schacht, Assistant Professor, Agronomy,Lincoln; Patrick Reece, Associate Professor,Agronomy, Panhandle Research and ExtensionCenter, Scottsbluff.

Table 2. Crude protein and digestibility of winter diet samples from sandhills range listed bysummer grazing treatment, DM basis.

Control June grazed July grazed

Stocking ratea

Item 0 33 67 100 33 67 100

CP 5.4 5.6 5.7 5.5 5.5 6.0 6.0IVDMD b 55.1 54.4 54.3 53.9 53.8 53.1 53.7

aPercentage of recommended annual stocking rate (e.g. % of .6 AUM’s/acre).bControl vs. grazed (P = .09).

diets was affected (P < .05) by year butwas not affected by winter samplingtime.

In Table 2, mean crude protein anddigestibility values are listed by sum-mer treatment. Diets collected fromcontrol pastures tended to be higher (P

= .09) in digestibility than pasturesgrazed during the summer. There wereno significant summer treatment ef-fects on CP levels in winter diets.

Summer grazing treatments did nothave a significant impact on winter dietquality of Sandhills range. However,


Ruminal Degradation of Rubisco by Beef CattleGrazing Switchgrass and Big Bluestem

Dan VaughnWalter SchachtLowell Moser

Robert GrayboschTerry Klopfenstein1

Passage of bundle sheathcells in warm-season grasses fromthe rumen appears to be a mecha-nism allowing proteins to escaperumen degradation.

Summary

This two-year study was conductedon monocultures of switchgrass andbig bluestem to: (1) determine the con-centration of the protein ribulose-1,5-bisphosphate carboxylase (Rubisco),found only in the bundle sheath cells ofwarm-season grasses, in omasal, mas-ticate and fecal samples of grazingcattle; and (2) estimate rumen-escapeRubisco via bundle sheath cells. A quan-tifying enzyme-linked immunosorbentassay, along with estimates of rumen

and lower tract digestibilities, indi-cated as much as 11% of Rubisco in bigbluestem and 13% in switchgrass es-caped rumen degradation and was ab-sorbed in the lower tract. Realizingthese amounts of escape Rubisco rep-resent a significant level of solubleprotein, bundle sheath cells may pro-vide a mechanism allowing solubleprotein to escape ruminal degrada-tion.

Introduction

Significant amounts of dietary pro-tein in warm-season grasses pass fromthe rumen undegraded and are digestedand absorbed in the lower tract. Previ-ous research indicates bundle sheathcells in warm-season grasses may playa role in protein escape from the rumen.In warm-season grasses, Rubisco, theenzyme responsible for CO

2 fixation in

C3 photosynthesis, is located exclu-sively in bundle sheath cells. In previ-ous research, Rubisco was detected inomasal and fecal samples from cattlegrazing monocultures of switchgrass orbig bluestem. This past research

hypothesized that a portion of theingested Rubisco and associated pro-teins escape the rumen via bundle sheathcells which are structurally weakenedby rumen activity. They proposed theproteins are digested in the lower tractfollowing further degradation of theweakened bundle sheath cells. The hy-pothesis has not been verified, nor hasthe amount of Rubisco escaping therumen or disappearing in the lower tractbeen estimated.

The purpose of this study was todetermine if passage of bundle sheathcells from the rumen represents a mecha-nism for protein to escape from therumen. The specific objectives were to(1) determine the concentration ofRubisco in masticate, omasal and fecalsamples of ruminally-fistulated beefcattle grazing switchgrass and bigbluestem; and (2) estimate rumen-es-cape Rubisco via bundle sheath cells.Presence of Rubisco in a sample wouldindicate presence of intact bundle sheathcells, as the highly soluble Rubisco isfound only in bundle sheath cells ofwarm-season grasses.


Procedure

Monocultures of switchgrass and bigbluestem were grazed in the summersof 1995 and 1996 at the University ofNebraska Agricultural Research andDevelopment Center near Mead,Nebraska. Each pasture was grazed bythree ruminally fistulated cows (1,350lb) in 1995 and four ruminally fistu-lated steers (650 lb) in 1996. Pastureswere grazed at vegetative and late elon-gation/early reproductive stages foreach grass species. Cattle strip-grazedeach pasture at each stage of develop-ment for six days and samples werecollected on day 7. Animals weremoved daily and herbage allowance onthe switchgrass and big bluestemmonocultures remained above 330lbs AUD-1 in 1995 and above 440 lbsAUD-1 in 1996.

Rumen contents of each animal wereevacuated and samples of the omasalcontents were obtained by hand throughthe reticulo-omasal opening on day 7.Before replacing the rumen contents,masticate samples were collected aftera 30-minute grazing period to representthe undegraded forage being grazed.Fecal samples also were obtained onday 7 of the grazing period.

Sodium dodecyl sulfate polyacryla-mide gel electrophoresis (SDS-PAGE)along with a western immunoblottingprocedure were used to determine thepresence of Rubisco in the masticate,omasal and fecal samples. Enzyme-linked immunosorbent assay analysiswas performed to quantify Rubisco con-centrations.

Dry Matter Disappearance

Dry matter loss in the rumen andlower tract of the animal was estimatedfor calculation of Rubisco disappear-ance at the two points in the digestivetract. Acid insoluble ash (AIA) wasused as an internal marker for estima-tion of digestibility. Percentage drymatter disappearance (DMD) in the ru-men and lower tract was calculatedusing the following equations.

DMD in rumen = 100 - 100 (% AIAmasticate sample / % AIA omasalsample)

DMD in lower tract = 100 - 100 (%AIA omasal sample / % AIA fecalsample)

Calculations of Rumen-Escape Rubisco

Rumen-escape Rubisco, or Rubiscodisappearing in the lower tract (%RERuBPCase), was calculated (+ S.E.) asa percentage of total Rubisco using thefollowing equation:

% RE Rubisco =

(OR x 1 - RD) - (FR x 1 - RD x 1 - LD)

MR

where OR is omasal Rubisco concen-tration, RD is rumen digestibility, FR isfecal Rubisco concentration, LD is lowertract digestibility and MR is masticateRubisco concentration. The equationaccounts for dry matter (DM) loss in therumen and lower tract so the estimate ofpercentage rumen-escape Rubisco isbased on intake Rubisco.

Concentrations of Rubisco escapingthe entire digestive tract (%TE Rubisco)was estimated (+S.E.) as a percentageof total Rubisco using the followingequation:

%TE Rubisco =

FR x (1 - RD) x (1 - LD)

MR

where FR is fecal Rubisco concentra-tion, RD is rumen digestibility, LD islower tract digestibility and MR is mas-ticate Rubisco concentration. FecalRubisco concentrations represent thepercentage of intake Rubisco found inthe feces.

Results and Discussion

Extraction of N-containing substratesfrom the switchgrass and big bluestemsamples was very effective. Over 97%of the N was extracted consistentlyfrom the masticate, omasal and fecalsamples. Rubisco was detected inundegraded leaf, masticate and omasalextracts of switchgrass and big bluestemby western immunoblotting followingSDS-PAGE. Negligible amounts ofRubisco were detected in the fecal ex-tracts of switchgrass and big bluestem.Identification of Rubisco in omasalsamples of big bluestem and switch-grass verified previous research results.

Concentrations of Rubisco in masti-cate, omasal and fecal samples (Table1) were used in conjunction with esti-mates of DM loss in the rumen andlower tract to calculate Rubisco disap-pearance in the rumen and lower tract(Table 2). Disappearance of bigbluestem Rubisco in the rumen wasbetween 63.6% and 65.3%, except inthe 1996 vegetative stage. Percentageswitchgrass Rubisco disappearing inthe rumen was 15 to 25% lower than forbig bluestem, except for the 1996 veg-etative samples. Percentage switchgrassRubisco disappearance of the 1996 veg-etative samples was nearly two-foldhigher than the other switchgrasssamples. The relatively high amountsof Rubisco disappearing in the rumenfor the switchgrass and big bluestemvegetative samples in 1996 cannot beexplained.

Disappearance of Rubisco in thelower tract ranged from 10.6% to 19.5%for big bluestem and 13.3% to 39.6%

Table 1. Percentage Rubisco concentrations (+S.E.) in omasal, masticate and fecal samples of beefcattle grazing big bluestem or switchgrass in vegetative or elongation/reproductive stagesof growth.

Vegetative Elongation/Reproductive

Species 1995 1996 1995 1996

----------------------------------------- % ---------------------------------------------

Big bluestemOmasal 2.9 (.06) 5.0 (.30) 3.7 (.28) 4.3 (.28)Masticate 3.9 (.26) 11.9 (3.0) 5.2 (.96) 6.6 (.96)Fecal 3.2 (.16) 3.2 (.24) 4.2 (1.3) 2.6 (.20)

SwitchgrassOmasal 4.6 (.12) 3.5 (.20) 4.8 (.16) 4.6 (.38)Masticate 5.5 (.70) 12.3 (2.8) 5.0 (.10) 7.2 (2.2)Fecal 4.1 (.16) 1.5 (.26) 4.4 (.16) 2.1 (.28)


for switchgrass over stages of growthand years. Disappearance of Rubisco inthe lower tract indicates a significantportion of ingested bundle sheath cellsescape the rumen to be degraded in thelower tract. Bundle sheath cells enter-ing the lower tract may be structurallyweakened due to rumen activity andtheir contents, including Rubisco, maybecome available to digestive enzymesin the lower tract. Mean percentages ofRubisco escaping the entire digestivetract were above 10% for both species,except for the 1996 vegetative samples.A portion of bundle sheath cells appar-ently escaped the entire digestive tract.

Our results indicate a significant partof intake Rubisco escapes rumen degra-dation via bundle sheath cells and dis-appears in the lower tract. The Rubisco,which we used as a marker of bundlesheath cell integrity, represents only aportion of the available protein in bundlesheath cells. Because concentration ofRubisco in bundle sheath cells has notbeen determined for switchgrass andbig bluestem, we cannot accurately es-timate amount of protein escaping therumen via these cells. Composition ofbundle sheath cells and total solubleprotein relative to Rubisco, however,has been determined for such warm-season, agronomic grasses as corn andmillets. For example, we used theRubisco concentrations in millet, alongwith our values of rumen-escapeRubisco, to determine if the amount ofrumen-escape protein via bundle sheathcells was biologically significant. Esti-mates of rumen-escape protein rangedfrom 7% to 32% of the total crude

protein content for switchgrass and 7%to 14% for big bluestem. Rumen-es-cape protein estimates were lower forthe vegetative stage and higher for theelongation/reproductive stages. Ourestimates of escape protein via bundlesheath cells are about 50% less thanestimates of total rumen-escape proteinfor big bluestem and switchgrass re-ported in the literature. Our values arelow compared to other estimates par-tially because we are not accounting forthe non-bundle sheath cell protein thatescapes. However, our example calcu-lations indicate that the bundle sheathcell mechanism may account for asmuch as 50% of the rumen escape pro-tein in big bluestem and switchgrass.

In conclusion, passage of bundlesheath cells from the rumen appears toprovide a mechanism which allows pro-tein escape from the rumen. Also, ourresults indicate Rubisco and associatedproteins found in a portion of the escap-ing bundle sheath cells disappear in thelower tract. The amount of Rubisco andassociated proteins escaping the rumenvia bundle sheath cells could representa significant portion of rumen-escapeprotein in big bluestem and switch-grass. Understanding the mechanismsinvolved in rumen escape protein shouldimprove the efficiency of livestock feed-ing systems and assist in the selection ofimproved forage species.

1Dan Vaughn, graduate student, WalterSchacht, Assistant Professor, Lowell Moser,Professor, Agronomy, Lincoln; Robert Graybosch,Research Geneticist, USDA/ARS, Lincoln; TerryKlopfenstein, Professor, Animal Science, Lincoln.

Table 2. Percentage intake Rubisco (+S.E.) disappearing in the rumen and lower tract, and escapingthe entire digestive tract of beef cattle grazing big bluestem or switchgrass in vegetative orelongation/reproductive stages of growth.

Vegetative Elongation/Reproductive

Species 1995 1996 1995 1996

----------------------------------------- % ---------------------------------------------

Disappearing in rumenBig bluestem 63.6 (3.4) 80.8 (6.8) 65.3 (13.3) 63.8 (9.0)Switchgrass 49.6 (9.6) 84.1 (2.3) 39.3 ( 8.9) 47.9 (9.4)

Disappearing in lower traceBig bluestem 14.4 (.42) 10.6 (2.4) 14.7 ( 5.7) 19.5 (5.3)Switchgrass 21.7 (8.9) 13.3 (2.4) 27.1 ( 3.8) 39.6 (.54)

Escaping entire traceBig bluestem 22.2 (3.0) 9.1 (3.4) 19.9 ( 7.6) 14.2 (2.3)Switchgrass 28.7 (1.0) 4.8 ( .9) 33.5 ( 6.0) 21.8 (3.2)

EvaluatingStress in Calves

Weaned atThree Different

Ages

Andrea BuenoTodd G. Cappel

Chuck StoryMark Dragastin

Rick RasbyEdd Clemens1

Calves weaned in October(210 days) exhibited less chronicstress, more prolonged endocrineresponses, and greater weight gainsthan calves weaned in August (150days) and December (270 days).

Summary

Trials were conducted to evaluatethe effects of weaning calves at 150,210 and 270 days of age (i.e. August,October and December, respectively).A total of 75 Angus x MARC II heiferscalves were used in this study. Heiferswere bled on the day of weaning andagain at 2, 7, 14 and 28 days afterweaning. Blood was analyzed for dif-ferential WBC, cortisol, T

3 and glu-

cose. Weight changes were recorded.The data suggests October weanedcalves (210 days) had both greaterblood cortisol and glucose at days 7, 14and 28 post-weaning and greater weightgains when compared to calves weanedat 150 and 210 days of age.

Introduction

Cattle, which are animals of habit,become stressed when they experiencea novel or painful situation. Weaningcan be one such stressful change. Wean-ing involves not only psychological



stress due to separation, but also abruptchanges in the calf’s environment, nutri-tion and social structure. Because ofthese variables, weaning could result ina considerable setback in a calf’s per-formance.

Studies on cattle suggest the physi-ological effects of separating a calffrom its mother may contribute to aperformance decrease several days af-ter weaning. Physiological effects maybe classified into three general catego-ries; gross clinical signs, blood compo-sition changes and endocrine interposedchanges.

The initial response to stress is arelease of hormones from the adrenalgland. The adrenal hormone cortisolfunctions to increase gluconeogenesisresulting in increased blood glucose,decreased glucose uptake by the tis-sues, decreased protein synthesis andan increased immune-defense system(increase in WBC count).

Triiodothyronine (T3) responds to

stress by calibrating the metabolic stateof the animal, which means body heatproduction is altered, allowing thestressed animal to adapt to the environ-ment. Thus, both rapid defense systems(cortisol) and long-term adaptationmechanism (T

3) are effected by stress.

In this study, cortisol, T3, glucose,

differential WBC and weight changeswere analyzed to determine the effectsof weaning at 150, 210 and 260 days ofage.

Procedure

Animals and management

This research was conducted using75 Angus x MARC II crossbred heifercalves. All animals were managed atthe University of Nebraska, Dalbey-Halleck Farm near Virginia, Nebraska.Calves were randomly allotted to one ofthree weaning groups based on age (150,210 and 260 days; August, October andDecember weaning, respectively). Inaddition, control groups of non-weanedcalves were assigned to August andOctober weaning groups. At weaning,all calves were separated from theirdams and taken to a post-weaning penwith free access to grass hay and water.After three days they were fed corn and

Figure 1. Plasma cortisol means observed in the calves at the day of weaning and at 2, 7, 14 and 28days after weaning for August, October and December groups.

Figure 2. Plasma glucose means observed in the calves at day of weaning and at 2, 7, 14 and 28 daysafter weaning for August, October and December groups.

a protein supplement to gain 1.25 to 1.5pounds per day. The non-weaned calvesremained with their mother.

Blood sampling

Blood samples were collected viajugular venipuncture on the day of wean-

ing (day 0) and days 2, 7, 14 and 28 afterweaning from both weaned and non-weaned calves. Plasma samples wereanalyzed for T

3 and cortisol, using radio-

immunoassay and glucose, and usingautomated, colorimetric determination(Auto Analyser I). Blood smears were

7

6

5

4

3

2

1

0

Pla

sma

cort

isol

, ug/

dl

0 2 7 14 28

Day

August October December

100

80

60

40

20

0

Pla

sma

gluc

ose,

mg/

100m

l

0 2 7 14 28

Day



December weaned calves at day 2 post-weaning (P<0.001), but continued toincrease and remain high only inOctober-weaned calves (P<0.01-Figure 1). Plasma cortisol valuesdecreased at days 7 and 14 for theAugust weaned calves (P<0.05). Plasmaglucose concentration changes werenot as dramatic as those of cortisol(Figure 2). Blood glucose concentra-tions for October calves continued toincrease and remain high throughoutthe post-weaning period, while concen-trations for August and most notice-ably December weaning decreased.

Concentrations of plasma T3 were

highest in the August and lowest in theDecember calves at the time of weaning(P<0.05 - Figure 3). Plasma T

3 de-

creased (P<0.05) in each age group, butwere similar at day 2 post-weaning.Thereafter, post-weaning concentra-tions of T

3 were generally reflective of

the environmental temperature duringthat post-weaning period. Calvesweaned in the warm August days main-tained the lower T

3; calves weaned in

December exhibited higher T3 concen-

trations.Figure 4 presents the data for the

Neutrophil: Lymphocyte ratio (WBCcount). Calves weaned in August dem-onstrated the most dramatic increase inN: L ratio at day 2 post-weaning(P<0.05), and continued to maintain thehigher ratio throughout the post-wean-ing period. The October and Decemberweaned calves had similar, but lower,N: L ratio’s during the post-weaningperiod.

Figure 5 illustrates the weight gainof the calves from weaning (day 0) tothe completion of the trial (day 28) foreach age group, as well as for the con-trol (non-weaned) calves. Mean weightgains were greater (P<0.05) for October(67.5 lb) weaned calves compared toAugust (52.2 lb - P<0.1) and December(43.7 lb) weaned calves for the first 28days post-weaning.

We know stress response increasesthe animals resistance to stress. Theoverall effects of stress can be favor-able or not, depending on the animal’sperceptions. In an acute stage, the stressresponse is, in general, beneficial. On

made from each sample to determinedifferential white blood cell counts.


Significant differences (P<0.01) ex-isted for most blood parameters due to

age of weaning. Mean values for eachblood parameter are presented in Fig-ures 1 through 4. Non-weaned calvespresented no significant changes in theconcentration of the blood parametersanalyzed over the 28-day trial. Plasmacortisol increased for October and

Figure 3. Plasma T3 means observed in the calves at the day of weaning and at 2, 7, 14 and 28 daysafter weaning for August, October and December groups.

Figure 4. Neutrophil:Lymphocyte ratio means observed in the calves at the day of weaning, and atday 2, 7, 14 and 28 after weaning for August, October and December groups.


180

160

140

120

100

80

60

40

20

0

Pla

sma

T 3, n

g/d

l

0 2 7 14 28

Day


0.6

0.5

0.4

0.3

0.2

0.1

0

N:L

ra

tio

0 2 7 14 28

Day



the other hand, if the stress is too in-tense, it may be harmful to the calves. Inthis study, calves weaned in October(210 days) had higher concentrations ofcortisol and glucose on days 7, 14 and28 after the weaning; however weightgain was significantly greater in thisgroup of calves compared to calvesweaned in August (150 days) andDecember (270 days). Therefore, forOctober-weaned calves, the stress wasnot severe enough to decrease animalperformance and actually induced afavorable response increasing theirweight gains as compared with the othertwo groups.

1Andrea Bueno, Todd Cappel and ChuckStory, graduate students. Rick Rasby and EddClemens, Professors, Animal Science, Lincoln;Mark Dragastin, manager, Dalbey-Halleck ResearchFarm, Virginia.

Figure 5. Changes in weight observed in weaned and non-weaned calves in August, October andDecember groups.

Induction of Estrus in Anestrous SuckledBeef Cows

Karol FikeMichael DayKeith InskeepJames Kinder

Paul LewisRobert ShortHarold Hafs1

Anestrous beef cows can be in-duced to initiate estrous cyclespostpartum by short-term treatmentwith an intravaginal implant ofprogesterone.

Summary

Suckled anestrous beef cows (n=362)received either: 1) an intravaginal im-plant containing progesterone for 7days plus a 1 mg injection of estradiolbenzoate 24 to 30 hours after implantremoval; 2) an intravaginal implantcontaining progesterone for 7 days; 3)a sham implant for 7 days plus a 1 mginjection of estradiol benzoate 24 to 30hours after implant removal; or 4) a

sham implant for 7 days. Treatmentwith progesterone resulted in resump-tion of luteal function in suckledanestrous beef cows with most cowsdeveloping corpora lutea with a typi-cal lifespan, whereas treatment withestradiol benzoate enhanced the ex-pression of estrus.

Introduction

Treatment with progestins, such asmelengestrol acetate, norgestomet orprogesterone (P

4) induces estrous cycles

in some anestrous cattle. Progestin pre-treatment alters uterine function afterthe first postpartum ovulation and yieldsnormal duration of luteal function.Treatment with estradiol benzoate (EB)following progesterone withdrawal en-hances incidence of ovulation in post-partum cows.

The objectives of this experimentwere to determine whether: 1) treat-ment with progesterone via an intrav-aginal implant induces estrus andformation of corpora lutea (CL) withtypical lifespans; and 2) treatment with

estradiol benzoate (EB) followingprogesterone removal improves ratesof behavioral estrus and formation ofCL with typical lifespans in suckledanestrous beef cows.

Procedure

Suckled anestrous beef cows (n=362)from 25 to 50 days postpartum wereused in four locations (Montana, n=97;Nebraska, n=101; Ohio, n=92; and WestVirginia, n=72). On average, cows werein their third parity during the experi-ment. Within each location, cows werestratified by calving date and assignedto receive one of four treatments. Be-ginning on day 0 (day of treatmentinitiation) cows were treated with oneof the following: 1) an intravaginalimplant containing P

4 (EAZI-BREED™

CIDR®, InterAg, Hamilton, NewZealand) for 7 days plus an injection of1 mg of EB (CIDIROL®, InterAg,Hamilton, New Zealand) 24 to 30 hoursafter progesterone removal (P

4 + EB);

2) an intravaginal implant containing P4

for 7 days (P4); 3) a sham implant for 7

70

60

50

40

30

20

10

0

Wei

ght g

ain,

lb


weaned non-weaned October x December weaned group (P<.05)October weaned x non-weaned (P<.01)


days plus an injection of 1 mg of EB 24to 30 h after device removal (EB); or 4)a sham implant for 7 days (control). Theintravaginal implant contained 1.9 g ofP

4 and was designed to release amounts

of P4 typical of the concentration found

circulating during the luteal phase ofthe estrous cycle.

Body condition scores, based on a 1to 9 scoring system (1 = thin and 9 =fat), were assessed for each animal onthe day of implant insertion. Mean bodycondition scores of cows within eachlocation were: Montana, 4.6; Nebraska,4.1; Ohio, 4.7; West Virginia, 5.0.

Blood Collection and Response toTreatment

Blood samples were collected onday -7, 0, 8, 15 and 22 (day 0 = implantinsertion) via the jugular or tail vein andwere used to assess circulating concen-tration of P

4 as an indicator of luteal

function. Based on changes in concen-tration of P

4 during the experiment,

cows were fitted into one of the follow-ing response categories: 1) anestrus, 2)typical lifespan CL, 3) short-lived CL,4) late CL (CL formed late in experi-ment; not in response to treatment) and5) early CL (CL formed early in experi-ment; not in response to treatment).

Behavioral Response to Treatment

To detect onset of behavioral estrus,cows were observed for at least 30minutes twice daily at approximately12-hour intervals from day 0 to day 22of the experiment. Data were placedinto one of the following three catego-ries according to behavioral activity: 1)standing estrus, receptive to mountingby other cows; 2) active, cows exhib-ited sexual activity but would not standto be mounted; or 3) no estrus, cows didnot exhibit any signs of behavioral es-trus. Only data from day 0 to day 11 ofthe experiment regarding behavioralresponse to treatment were analyzed,with day 9 to day 11 being the periodwhen the majority of behavioralresponses to treatment were expectedto occur.

Conclusions from this experimentcould potentially alter current manage-

ment scenarios of cow-calf producers.Ultimately, producers are interested inthe number of cows exhibiting estrouscycles at the onset of the breeding sea-son and its effect on reproductive effi-ciency. Therefore, a table of predicteddata was compiled and analyzed inwhich numbers of cows that had formedCL by various criteria, reflecting ef-fects of treatment and natural resump-tion of estrous cycles, were considered.


Response to Treatment

The proportion of cows forming CLwith a typical lifespan increased (P <.001) in response to treatment with P

4

(Table 1), but location, body conditionscore, parity and number of days duringthe postpartum period had no effect.There were no interactions among treat-ments or location affecting formationof CL with a typical lifespan.

Behavioral Response to Treatment

The proportion of cows exhibitingestrus (i.e. standing estrus or estrousactivity) from day 0 to day 11 increased(P < .05) in response to P

4 treatment

(Figure 1). Similarly, EB increased (P <.001) the proportion of cows exhibitingestrus (Figure 1). Body condition score,parity and number of days during thepostpartum period did not affect theproportion of cows exhibiting estrus.However, there was an effect (P < .05)of location on proportion of cowsdetected in estrus. There were no inter-actions between P

4 and EB, location

and P4 or location and EB on the inci-

dence of estrus. The majority of cowsexhibiting estrus activity did so fromday 9 to day 11 of the experiment; fewcows exhibited estrus activity duringthe treatment period from day 0 today 8 (Figure. 1).

Table 1. Proportions of cows within each treatment that either formed a corpus luteum or did notinitiate luteal function.

Treatment

Responsea P4+EB EB P4 Control

Anestrus 15/93 (16%) 29/86 (34%) 28/92 (30%) 31/91 (34%)Typical lifespan CL 66/93 (71%) 17/86 (20%) 51/92 (55%) 15/91 (16%)Late CL 0/93 (0%) 14/86 (16%) 0/92 (0%) 6/91 (7%)Short-lived CL 4/93 (4%) 10/86 (12%) 5/92 (5%) 26/91 (29%)Early CL 8/93 (9%) 16/86 (19%) 8/92 (9%) 13/91 (14%)a Effect of the following variables on distribution of cows within response categories:P4, P < .001; EB, P > .10; P4 x EB, P > .10.


Figure 1. Number of cows within each treatment exhibiting estrous activity or standing estrusduring the experiment. Day 0 = initiation of treatments with intravaginal implants.

60

50

40

30

20

10

0

Num

ber

of c

ows

0 2 4 6 8 10 12 14 16 18 20 22

Day of experiment

F4+EBEBP4

Control


Predicted Proportions

A greater proportion (P < .01) ofcows treated with P

4 alone or in combi-

nation with EB were induced to formCL with a typical lifespan, comparedwith untreated cows (Table 2). Theeffect of P

4 was enhanced (P < .01) by

EB, but EB alone tended to reduce (P <.10) the proportion of cows formingeither a short-lived CL or CL with atypical lifespan, compared with un-treated cows (Table 2). The combina-tion of P

4 and EB increased the

proportion of cows forming CL in re-sponse to or during treatment (P < .01)and the proportion that had formed CLby the end of the experiment (P < .05),compared with untreated cows (Table2).

Our data reveal short-term treatmentof anestrous cows with P

4 can induce

earlier ovulation in some cows, increasethe percentage of cows exhibiting es-trous cycles during the breeding seasonand, presumably, increase the percent-age of cows conceiving at first service.Because these treatments can be used tosynchronize estrus in cows exhibitingestrous cycles, they provide the poten-tial to artificially inseminate a largeproportion of the herd at the same time.

Providing an exogenous source ofestradiol (i.e., EB) increased the pro-portion of cows exhibiting signs of be-havioral estrus. This estrus behaviorwas concentrated from day 9 to day 11of the experiment (Figure 1). A greaterproportion of cows treated with P

4 and

EB were either active or exhibited stand-ing estrus compared with cows treatedwith P

4 alone. While some cows in the

control group may have been inducedto exhibit estrous cycles by the concen-trated estrous activity of treated cows,more exhibited estrus activity beyondday 11 (Figure 1).

Because estradiol induces the preo-vulatory LH surge causing ovulation,we expected treatment with EB in addi-tion to P

4 would further increase the

proportion of cows forming CL. How-ever data analyzed in Table 1 showedEB did not enhance the response ofprogesterone in inducing onset of lutealfunction. From a practical standpoint,however, producers are interested in

the number of cows exhibiting estrouscycles at the onset of the breeding sea-son, which should enable more cows tobecome pregnant early in the season,resulting in fewer nonpregnant cows.Analyzing data as reported in Table 2allows for the consideration that somecows would have initiated estrous cyclesin the absence of progesterone treat-ment and compares the predicted effec-tiveness of each treatment with data forcontrol cows in inducing luteal func-tion by the end of the experiment. Basedon the predicted data in Table 2, agreater proportion of cows treated withP

4 and EB would be expected to form

short-lived or typical lifespan CL com-pared to untreated cows. Treatment withP

4 alone should increase the numbers of

cows developing CL with typical orshort lifespans. The data in Table 2indicate treatment with both P

4 and EB

should be more effective in inducingluteal function than other treatments.Combined treatment with P

4 and EB

may induce an adequate preovulatoryLH surge in a portion of cows withinsufficient endogenous estradiol pro-

Table 2. Predicted proportions of cows within each treatment group that formed a corpus luteumby various criteria.

Treatment

Response P4 +EB EB P4 Control

Formed or would have formed 7 8 7 5a CL during P4 treatmenta

Formed a CL with 59/78 (76%)** 17/70 (24%) 44/77 (57%)* 15/78 (19%)a typical lifespanb

Formed a short-lived or 63/78 (81%)** 27/70 (39%)† 49/77 (64%) 41/78 (53%)typical lifespan CLc

Total cows that formed a CL 78/93 (84%)** 43/86 (50%) 64/92 (70%) 54/91 (59%)by 4 d after the end of treatmentd

Total cows that formed a CL 78/93 (84%)* 57/86 (66%) 64/92 (70%) 60/91 (70%)a

by end of experimente

**Proportion differs from control: P < .01.*Proportion differs from control: P < .05.†Proportion differs from control: P < .10.aNumber of cows predicted to have formed a corpus luteum (CL) during treatment. Values for cows treatedwith sham devices were calculated from data for response 5 in Table 1. For EB, sham device (16/86) minusP4 implant (8/93) = 8. For control, sham (13/91) minus P4 (8/92) = 5. Value for P4-treated cows wasestimated as the mean of these values (6.5, rounded to 7).bProportion of cows that formed a CL with a typical lifespan. This proportion excludes from thedenominator cows that were in metestrus at treatment initiation or that formed or were predicted to forma CL while carrying a device (Early CL).cProportion of cows that formed either a CL with a typical lifespan or a short-lived CL. Early CL responseis excluded from the denominator.dProportion of cows in which a CL had formed by 4 d after the end of treatment.eProportion of cows that formed a CL by the end of the experimental period.

duction, increasing the number of cowsdeveloping CL.

Treating postpartum beef cows dur-ing lactational anestrus with progester-one and estradiol benzoate inducedestrus and the formation of corporalutea with typical lifespans. Theseresponses in anestrous cows canincrease the percentage of cows exhib-iting estrous cycles at the onset of thebreeding season and may result in bothmore cows being maintained on a yearlycalving interval and fewer cows beingculled from the herd. Because thesetreatments can be used to synchronizeestrus in cows, they provide the poten-tial for artificial insemination of a largeproportion of the herd at the same time.

1Karol Fike, former graduate student; MichaelDay, Associate Professor of Animal Science, OhioState University; Keith Inskeep, Professor of AnimalScience, West Virginia University; James Kinder,Professor of Animal Science, University of Nebraska;Paul Lewis, Professor of Animal Science, WestVirginia University; Robert Short, Professor ofAnimal Science, USDA ARS, Livestock and RangeResearch Laboratory, Miles City, MT; Harold Hafs,Professor of Animal Science, Rutgers University.


A Novel Estrous Synchronization Program for BeefCattle Using Melengestrol Acetate

Programs incorporating progestins suchas norgestomet, MGA and (or) proges-terone can also induce estrous cycles inanestrous females. Treatment with com-mercially used doses of a progestin inthe absence of corpora lutea results indevelopment of persistent ovarian fol-licles. While reduced fertility is associ-ated with ovulation of persistent ovarianfollicles, fertility can be improved withshort-term progesterone treatment toinduce regression of persistent ovarianfollicles.

Development of a relatively inex-pensive estrous synchronization pro-gram limiting animal handling withoutcompromising pregnancy rates (num-ber females pregnant/number femalestreated) would benefit the beef indus-try. We hypothesized that estrous syn-chronization of beef females using MGAand an injection of progesterone andestradiol would maximize pregnancyrates as compared with use of MGAalone or two injections of PGF

2α.

Procedure

Angus x Gelbvieh heifers (n = 52)and mature composite (MARC III;n=288) and Angus x Gelbvieh cows (n= 39) from the beef physiology herdwere used during two years (1995 and1996). Females were blocked by breedand were stratified by calving date andassigned to receive one of the follow-ing: 1) MGA (.5 mg/hd/day) for 18 daysplus an injection of 200 mg progester-one and 1 mg estradiol in sesame oil onday 11 (MGA+P

4; day 0 = first day of

MGA feeding); 2) MGA for 18 daysplus an injection of sesame oil on day11 (MGA); or 3) two injections of PGF

2aα(25 mg; Lutalyse® Sterile Solution,Upjohn, Kalamazoo, MI) on day 7 and

17 (PG).During the experiment, females were

maintained in bromegrass pastures.During 1995, 2 lb per animal of forage-based pellets containing MGA were fedwith either range cubes or corn (1.5 to 2lb/hd/day) for females in the MGA orMGA+P

4 treatment groups, while fe-

males in the PG treatment group re-ceived range cubes (3.5 to 4 lb/hd/day).Because feed consumption for femalestreated with MGA was inconsistentthroughout the treatment period, mecha-nisms such as feeding molasses andkeeping cattle off pasture overnight wereused to help maintain MGA consump-tion.

To alleviate variation in MGA con-sumption, changes were made in nutri-tional management during the secondyear. Salt was restricted from all cattle18 days before MGA feeding. Soybeanhull pellets (2 lb/hd/day) were fed 13days before MGA feeding to acclimatecattle to bunks. Three days before MGAfeeding, soybean hull pellets contain-ing salt (.13 lb/lb feed) were provided toall cows (2 lb/hd/day). Soybean hullpellets (2 lb/hd/day) containing salt andMGA (.25 mg/lb) were fed during thetreatment period to females in the MGAand MGA+P

4 treatment groups, while

females in the PG group continued toreceive pellets (2 lb/day) consisting ofonly soybean hulls and salt. Restrictionof salt intake was implemented to stimu-late a salt consumption desire. Includ-ing salt in the feed just prior and duringMGA feeding was expected to decreaseconsumption variation of MGA as wellas maintain MGA consumption overthe 18-day treatment period. From endof treatment until the end of estrousdetection and AI, all females were fed


Karol FikeMichael Wehrman

Brad LindseyEllen BergfeldEric Melvin

Jorge QuintalEraldo ZanellaFreddie KojimaJames Kinder1

Estrous cycles can be synchro-nized among anestrous and estrualbeef females by feeding melen-gestrol acetate for 18 days and in-jecting progesterone and estradiol7 days before end of MGA feeding.

Summary

Estrous synchronization rate andconception and pregnancy rates to AIwere evaluated following three estroussynchronization protocols for beefcattle. During 1995 and 1996, heifersand cows (n = 379) received either: 1)melengestrol acetate (MGA) for 18 daysplus an injection of progesterone andestradiol in oil 7 days before end oftreatment; 2) MGA for 17 days; or 3)two injections of PGF

2α 10 days apart.

The greatest pregnancy rates (numberconceived/number treated) among bothanestrous and estrual females wereachieved following treatment with MGAand an injection of progesterone andestradiol.

Introduction

Estrous synchronization programs inbeef herds can condense labor duringbreeding and calving seasons as well asproduce calves more uniform in weight.


pellets containing soybean hulls andsalt. During 1995 and 1996, MGA failedto suppress ovulation during treatmentin 20 of 132 (15.2%) and 13 of 118(11%) of females treated with MGA orMGA+P

4. In 1996, body condition

scores (1 = thin, 9 = fat) were assessedfor all animals on day 0 and day 17 ofthe experiment.

Blood samples were collected onday 0 (initiation of MGA feeding), 7and 17 of the experiment to character-ize progesterone concentrations anddetermine estrual status (exhibiting es-trous cycles or anestrus). Blood samplescollected on day 0, 7, 9, 11, 13, 15 and17 were used to determine concentra-tion of estradiol in circulation.

Females with concentrations ofprogesterone > 1 ng/ml of serum on day0, 7 or 17 were considered to have lutealfunction and were categorized as es-trual. All other females were catego-rized as anestrus.

Females were observed for behav-ioral estrus every 6 hours from day 17(last day of MGA feeding or 2nd injec-tion of PGF

2α ) until day 24 with the aid

of K-Mar devices and epididymal li-gated bulls. Females exhibiting signs ofestrus were bred by AI 6 to 12 hoursfollowing detection. Uterine ultrasonog-raphy was performed 35 to 40 daysfollowing AI to determine conceptionrate.


Concentration of Estradiol

Concentration of estradiol was el-evated during or increased near the endof treatment among both anestrous andestrual females treated with only MGA(Figures 1 through 4). Among estrualfemales, corpus luteum regressionwould have occurred at random duringthe treatment period. Treatment withMGA in the absence of a corpus luteumallows for increased pulse frequency ofLH, resulting in development of persis-tent ovarian follicles and associatedelevated concentrations of estradiol.Random initiation of development ofpersistent ovarian follicles correspond-ing with onset of luteal regression likelyoccurred in the present study. As indi-

Figure 1. Concentration of estradiol among anestrous composite females during treatments tosynchronize estrous cycles. Uncommon superscript letters within day indicate differencesacross treatment groups (a,b,c P < .05).

cated by the elevated concentration ofestradiol in circulation on day 17 of theexperiment, a majority of estrual fe-males likely had persistent folliclespresent in their ovaries at cessation ofMGA feeding.

Generally, concentrations of estra-diol were greater during the treatmentperiod among anestrous females fedMGA as compared with the PG group.This indicates treatment of anestrousfemales with a progestin such as MGAis able to elicit changes, presumably in

secretion of LH, and subsequently inovarian follicle development and se-cretion of estradiol.

Among anestrous females of bothbreeds and estrual composite femalesin the MGA+P

4 group, concentrations

of estradiol decreased from day 11 today 13. Administration of progesteroneand estradiol in oil to females of thisgroup occurred on day 11 and was ex-pected to induce regression of persis-tent ovarian follicles. The sharp declinein concentration of estradiol among

10

8

6

4

2

017

β-es

trad

iol (

pg/m

l)0 7 9 11 13 15 17

Day of experiment

MGA+P4 MGA PG

PGPG

P4/E2

a

a

a

a

a

a

a

aa a

bb

ab

b

b

b

bb

b

b

b

Figure 2. Concentration of estradiol among anestrous Angus x Gelbvieh females during treat-ments to synchronize estrous cycles. Uncommon superscript letters within day indicatedifferences across treatment groups (a,b,c P < .05;x,y P < .10).

MGA+P4 MGA PG

P4/E2

10

8

6

4

2

0

17β-

estr

adio

l (pg

/ml)

0 7 9 11 13 15 17

Day of experiment

PG PG

b

b

b

b

b

bxy

x

ay

ax

aaa

a

a

a

a

b

c


on day 7. The increase in estradiolconcentration on day 9 would coincidewith development of the ovulatory fol-licle. Absence of an estradiol increaseamong anestrous females on day 9 con-firms these females were anestrous dur-ing the treatment period.

Time to estrus

Treatment and estrual status inter-acted (P = .02) to affect time to estrus.Among anestrous females, interval fromtreatment cessation to onset of estruswas similar among females in the PG ascompared with the MGA+P

4 group

(Table 1). Compared to females treatedwith MGA, interval from treatment ces-sation to onset of estrus was shorter (P= .006) among females treated withMGA+P

4 and tended (P = .09) to be

shorter among females treated with PG.Among estrual females, interval fromtreatment cessation to onset of estruswas similar among females in the MGAand MGA+P

4 groups and MGA and PG

groups, but was shorter (P = .05) infemales treated with PG as comparedwith those treated with MGA+P

4.

We expected treatment with MGAalone would result in the shortest inter-val to estrus onset due to the advancedstage of ovarian follicle development atthe time of treatment withdrawal. Per-haps ovarian follicles of some animalswere not at an advanced stage of devel-opment at treatment withdrawal, butrather had undergone natural atresiabefore cessation of MGA feeding.

Estrous synchrony rate

Treatment and estrual status inter-acted (P < .001) to affect estrous syn-chrony rate (number in estrus/numberin group; Table 1). Among anestrusfemales, a greater (P < .001) percentageof females in the MGA and MGA+P

4

groups exhibited estrus following treat-ment compared with females in the PGgroup. There tended to be a greater (P =.10) percentage of anestrous females inthe MGA+P

4 group exhibiting estrus

following treatment compared with theMGA group. Among estrual females, agreater percentage of females in the PG


anestrous and estrual females of com-posite breeding in the MGA+P

4 group

indicates that regression of persistentovarian follicles was achieved. It isunclear why estrual females of Angus xGelbvieh breeding did not have a simi-lar estradiol concentration decline fol-lowing the injection of progesteroneand estradiol. Perhaps a significant por-tion of these females were in the lutealphase of their estrous cycle at the timeof the injection (on day 11) such that nopersistent ovarian follicles were present

to regress.Concentration of estradiol increased

on day 9 among estrual females in thePG group. The especially large increasein concentration of estradiol on day 9among estrual Angus x Gelbvieh heif-ers was apparent among most femalestreated with PGF

2α on day 7. Corpus

luteum regression, and initiation of thefollicular phase of the estrous cycle,would have occurred among femalestreated with PGF

2α that had a corpus

luteum capable of responding to PGF2α

Figure 4. Concentration of estradiol among estrual Angus x Gelbvieh females during treatmentsto synchronize estrous cycles. Uncommon superscript letters within day indicate differ-ences across treatment groups (a,b,c P < .05).

Figure 3. Concentration of estradiol among estrual composite females during treatments tosynchronize estrous cycles. Uncommon superscript letters within day indicate differ-ences across treatment groups (a,b,c P < .05; x,y P < .10).

MGA+P4 MGA PG

P4/E2

10

8

6

4

2

0

17β-

estr

adio

l (pg

/ml)

0 7 9 11 13 15 17

Day of experiment

PG PG

b

b b

b

b

ns nsns

a

ns

a

a

a

MGA+P4 MGA PG

P4/E2

10

8

6

4

2

0

17β-

estr

adio

l (pg

/ml)

0 7 9 11 13 15 17

Day of experiment

PG PG

bbyb

b

bb

ns

c

aby

ax

a

a

a

c

a

c

a

ab


Table 1. Estrous synchrony rates, conception and pregnancy rates to AI and time to behavioralestrus of females treated with MGA, MGA+P4, or PG.

Treatment

Item MGA MGA+P4 PG

Time to estrus, hours + SEMa

Anestrus 98.8 + 5.5x 76.7 + 5.7y 76.0 +12.4y

Estrual 75.7 + 6.2xy 79.8 + 4.4x 66.7 + 5.2y

Estrous synchrony rate, %a

Anestrusc 66.1x 81.4y 28.0z

Estruald 76.6x 89.9y 92.3y

Conception rate, % 50.0x 62.7xy 67.4y

Pregnancy rate, %b

Anestrus 33.9x 45.8x 16.0y

Estrual, 1995 44.2x 51.2xy 64.7y

Estrual, 1996 23.8x 76.9y 63.0y

aThere was a treatment x estrual status interaction (P < .001), therefore animals that were estrual andanestrus were analyzed separately.bThere was a treatment x estrual status interaction (P = .003), therefore animals that were estrual andanestrus were analyzed separately. Within estrual animals there was a treatment x year interaction (P =.06), therefore estrual animals within each year (1995 and 1996) were analyzed separately.x, y, zMeans within a row lacking a common superscript differ (P < .10).

(P = .02) and MGA+P4 (P = .07) groups

exhibited estrus following treatmentcompared with the MGA group; how-ever, estrous synchrony rates were simi-lar among females in the PG andMGA+P

4 groups. Body condition score,

age, number of days postpartum andyear neither affected nor interacted withtreatment to alter estrous synchronyrate.

Estrous synchronization rates aretypically improved with progestin-basedestrous synchrony programs because ofthe progestin’s ability to induce estrouscycles in anestrous females. In this study,23% of heifers and 48% of cows weredetermined to be anestrus prior to endof treatment. A greater percentage ofanestrous females in the MGA (66%)and MGA+P

4 (81%) groups were in-

duced to exhibit estrus following treat-ment compared with the PG group(28%). Among both anestrous and es-trual females, a greater percentage offemales in the MGA+P

4 group exhib-

ited estrus following treatment com-pared with MGA treatment alone. It isunclear why additional treatment withprogesterone and estradiol improvedestrous synchrony rate.

Inconsistent consumption of MGA,especially during 1995, likely resultedin lower estrous synchronization ratesamong females in the MGA+P

4 and

MGA groups. During 1995 and 1996,15 and 11 %, respectively, of femalesfed MGA appeared to have ovulated

during MGA feeding. During 1996, weattempted to alleviate problems regard-ing consumption of MGA by strategicrestriction and replacement of salt inthe rations. This change resulted in a 4% decrease in females ovulating duringMGA feeding. Females in this studywere maintained on pasture during theexperiment and MGA feeding occurredin May, a time of maximal forage growthin both 1995 and 1996. As a result,cattle were more likely to graze andbecome satiated on forages, decreasingconsumption of MGA. It is likely that ina drylot situation, estrous synchroniza-tion of beef females with MGA plusprogesterone and estradiol would resultin an improved estrous synchronizationrate.

Conception rate

Conception rate (number conceivedto AI/number AI’ed) did not differamong females in either the PG orMGA+P

4 groups, but was greater (P

=.04) among females in the PG as com-pared with MGA group (Table 1).

Conception rate to AI was accept-able among females in the PG andMGA+P4 groups. Conception rate offemales treated with MGA alone wasgreater than expected. Treatment withdoses of commercially used progestinsor low doses of progesterone in theabsence of a corpus luteum results indevelopment of persistent ovarian fol-

licles. Perhaps during the long-termMGA feeding, some persistent ovarianfollicles naturally regressed, allowingAI to coincide with ovulation of typi-cally developing ovulatory follicles,improving conception rates. The ele-vated concentrations of estradiolamong both anestrous and estrual com-posite and Angus x Gelbvieh femalesindicate large, persistent ovarian fol-licles were still present near the end ofthe treatment period.

Pregnancy rate

Treatment and estrual status inter-acted (P =.003) to affect pregnancy rate(number conceived to AI/number ingroup; Table 1). There was an effect (P< .05) of year on pregnancy rate amonganestrous females where pregnancy ratedid not differ among females in theMGA or MGA+P

4 groups, however, it

was greater among females in the MGA(P = .05) and MGA+P

4 (P < .01) groups

as compared with the PG group.Among estrual females, treatment

and year interacted (P =.06) to affectpregnancy rate. Among estrual femalesin 1995, pregnancy rate was greater (P= .05) among females treated with PGas compared with MGA, but did notdiffer from females treated withMGA+P

4. Among estrual females in

1996, pregnancy rate was greater (P <.01) among females treated withMGA+P

4 or PG as compared with MGA,

but did not differ among females treatedwith MGA+P

4 and those treated with

PG.Pregnancy rates to AI among

anestrous females were greater amongfemales in the MGA or MGA+P

4 groups

as compared with the PG group. Clearly,this advantage in pregnancy rate is dueprimarily to the improved rate of es-trous synchrony achieved followingtreatment with MGA versus PGF

2α .

During 1996, consistent consumptionof MGA was improved as compared to1995. This is evidenced by more fe-males consuming pellets for longer pe-riods of time following feeding, butdoes not readily explain the 20 % de-crease in pregnancy rate from 1995 to1996 in estrual females in the MGAgroup as compared with the 25% in-


crease in pregnancy rate of estrualfemales in the MGA+P

4 group. It is

important to recognize estrous syn-chronization of anestrous females withMGA plus progesterone and estradiolresults in greater pregnancy rates ascompared with PG, whereas amongestrual females, greater pregnancy ratescan be achieved following estrous syn-chronization with MGA plus progester-one and estradiol as compared withMGA alone. Ultimately, cow/calf pro-ducers are interested in maximizing

herd pregnancy rates. Because mostbeef herds would likely consist ofanestrous and estrual females, preg-nancy rates to AI would be maximizedmost effectively by estrous synchroni-zation with MGA plus progesteroneand estradiol.

For beef producers to achieve maxi-mal pregnancy rates, estrous synchro-nization rates, as well as conceptionrates, must be maximized. The presentstudy provides evidence that long-termfeeding of MGA, combined with an

injection of progesterone and estradiol,is effective in synchronizing estrus andachieving acceptable conception ratesto AI among both anestrous and estrualbeef females.

1Karol Fike, former graduate student. MichaelWehrman, former graduate student. Brad Lindsey,graduate student. Ellen Bergfeld, former graduatestudent. Eric Melvin, former graduate student. JorgeQuintal, former graduate student. Eraldo Zanella,graduate student. Freddie Kojima, former graduatestudent. James Kinder, Professor, Animal Science,Lincoln.

Effects of Luteinizing HormoneReleasing Hormone Antagonist On The

Bovine Corpus Luteum


Deb CloptonJorge Quintal

Freddie KojimaKarol FikeJim Kinder 1

Pulsatile luteinizing hormonerelease during the follicular phaseof the estrous cycle affects size andfunction of the corpus luteum andis important in achieving optimalcattle pregnancy rates.

Summary

The size and function of the corpusluteum were examined after adminis-tration of luteinizing hormone releas-ing hormone antagonist. Luteinizinghormone releasing hormone antago-nist was administered to three animalgroups starting: 1) 2 days before thepreovulatory luteinizing hormone surgeinducing ovulation; 2) at initiation ofthe preovulatory surge; and 3) 2 daysafter the preovulatory surge. Althoughsize and function of the corpus luteumwere suppressed in all treated groups,the greatest developmental suppres-sion occurred when luteinizing hor-mone release was blocked 2 days beforethe preovulatory surge of LH inducing

ovulation. Therefore, optimal preg-nancy rates in cattle may depend onpulsatile release of LH during the fol-licular phase of the estrous cycle inaddition to that secreted during andafter ovulation.

Introduction

The corpus luteum (CL) developsfrom an ovarian follicle following ovu-lation and secretes the progesteronerequired to support pregnancy. It hasbeen widely observed that luteinizinghormone (LH) is essential for the main-tenance of progesterone production bybovine luteal cells and recently shownthat LH pulse frequency is greater dur-ing the follicular phase than themidluteal phase of the estrous cycle. Ithas also been shown LH secretion is notrequired to maintain luteal function dur-ing the late luteal phase of a cow’sestrous cycle.

It is apparent the CL requires a spe-cific endocrine environment and devia-tions from this can be detrimental fornormal development of structure andfunction of luteal tissue. Presently, in-formation is scarce concerning the roleof LH secretion on luteal developmentand function during the follicular phaseand the periovulatory stages of the re-productive cycle. Treatment with lutein-

izing hormone releasing hormone(LHRH) antagonist to inhibit LH pulsesenables the role of LH pulses before,during and after the preovulatory surgeof LH on CL development and functionto be assessed.

Procedure

Experimental Protocol

This study used 21 postpubertal heif-ers of composite breeding (1/4 Here-ford, 1/4 Angus, 1/4 Redpoll, 1/4Pinzgauer; 972 lbs). Estrous synchronywas achieved with two injections ofprostaglandin F

2α (PGF2α ) administered

11 days apart. Heifers were randomlyassigned to one of the following treat-ments: 1) 5% mannitol injections serv-ing as a control; 2) LHRH-Antagonist(LHRH-Ant) starting 2 days before ini-tiation of the preovulatory LH surge;3) LHRH-Ant at initiation of the pre-ovulatory LH surge; and 4) LHRH-Antstarting two days after the preovulatoryLH surge. LHRH-Ant is a syntheticpeptide which selectively blocks LHsecretion. It was administered subcuta-neously to all treated groups every24 hours at 10µg/kg body weight untilday 7 of the estrous cycle. Preovulatorysurges of LH were experimentally


induced in all heifers by intravenousadministration of purified bovine LH(preovulatory LH surge = day 0) every20 minutes for 3 hours beginning 48hours after the second injection of PGF

2αin order achieve an initial concentra-tion of 100 ng/mL and to maintain aconcentration of 50 ng/ml. All follicleslarger than 5 mm were ablated by trans-vaginal procedures four days prior tothe second treatment of PGF

2α utilizingan ultrasonography probe equipped witha needle guide attachment. This en-sured synchrony of the waves of ova-rian follicular development and thatdominant follicles were at the samedevelopmental stage at corpus luteumregression.

Measurements and Sample Collection

Ovulation and development of theCL (size in mm) were monitored byultrasonography daily until day 12 ofthe estrous cycle and every other dayuntil day 28. Ovulation was identifiedas the disappearance of a large ovarianfollicle between two consecutive daysof ultrasonography. Starting at the timeof the second treatment of PGF

2a plasma

was obtained from blood samples col-lected every 12 hours until day 28 or thetime of subsequent behavioral estrusdetection, whichever occurred first.Concentrations of progesterone inplasma were analyzed by radioimmu-noassay (RIA). To verify accuracy ofexogenous LH treatment, serum wasobtained from blood samples collectedevery 20 minutes starting 2 hours be-fore the first LH treatment and ending 2hours after the last injection. Serumconcentrations of LH were analyzed byRIA.

Results

Size of Corpus Luteum

Size of the CL was largest (P<.01) incontrol group heifers and smallest inheifers in which LH release was blockedstarting 2 days before the preovulatorysurge of LH (Figure 1). Size of the CLin heifers in which LH release wasblocked, starting coincident with or 2days after the preovulatory surge ofLH, was less than controls but greater

Figure 1. Size of the corpus luteum in heifers treated with LHRH antagonist at different timesrelative to the preovulatory surge of LH and untreated controls (a,b,c=p<0.01).

Figure 2. Mean concentrations of progesterone in plasma from heifers treated with LHRH-antagonist at different times relative to the preovulatory surge of LH and untreatedcontrols. Control group is different from treated groups (P<0.01).

(P<.01) than in heifers in which LHsuppression started 2 days before thepreovulatory surge of LH. There was nodifference (P>.1) in size of the CLamong heifers in which LH suppressionstarted coincident with the preovula-tory surge of LH or 2 days after thepreovulatory surge of LH. Average sizeof CL was 9.5, 17.5, 21.6 and 28.8 mm(pooled SE = 0.43) for heifers in whichLH secretion was blocked starting48 hours before, at time of initiationor 48 hours after the preovulatory surgeof LH and control heifers, respectively.

Progesterone Concentrations

Compared with secretion of proges-

terone (area under the curve) from thecontrol group, secretion of progester-one was less (P<.01) in heifers whereLH release was suppressed prior to,during or after the LH surge (Figure 2).Arbitrary units under the progesteronerelease curve for heifers in which LHsecretion was blocked starting 48 hoursbefore, at the time of initiation or 48hours after the preovulatory surge ofLH and the control group were 19.6,41.6, 43.6 and 142.2, respectively. Therewas no difference in function of the CL(P>.1) as determined by arbitrary unitsof progesterone of heifers in the threegroups in which LH secretion wasblocked.

30

25

20

15

10

5

0

mm

1 3 5 7 9 11 13 15 17 19 21

Day of the Estrous Cycle

a

b

b

c

ControlAnt -2Ant 0Ant 2

14

12

10

8

6

4

2

0

ng

/ml

0 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21

Day of the Estrous Cycle

ControlAnt -2Ant 0Ant 2


Conclusions

Results from this study indicate LHpulses subsequent to the preovulatoryLH surge are necessary for develop-ment of a CL with similar size andfunctionality as those observed in con-trol heifers. The influence of LH secre-tion during late ovarian follicularmaturation and early luteal develop-ment appear to be additive in develop-ing CL of typical structural size. LHappears to have a differential effect ondevelopment and function of the CL incattle. The effects of LH on luteal func-tion, as evaluated by circulating con-centrations of progesterone, appear tobe more dramatic than the influence ofLH pulses on development of a CL oftypical structural size.

Inadequate numbers of LH receptorson both granulosa and thecal cells, dueto the absence of LH pulses prior to thepreovulatory surge, may account forthe smaller luteal structure in whichrelease of LH was blocked 48 hoursbefore the LH surge. Alternatively, thesmaller CL in these heifers may be theresult of altered populations of lutealcells. Small luteal cells possess func-tional LH receptors. Large luteal cellsdo not possess functional LH receptors;however, they will secrete large amountsof progesterone in the absence of LHstimulation. Therefore, it is possiblethat, in the absence of pulsatile LHsecretion during the late stages of ova-rian follicular maturation and earlyluteal development, small luteal cellsdo not receive the proper stimulus tosecrete progesterone and without LHsupport are not able to develop intolarge luteal cells that will secrete largeramounts of progesterone. Thecal,granulosal and luteal cells require pul-satile LH support during theperiovulatory stages of the estrous cyclefor development of a luteal structurewith typical size and steroidogenic ca-pacity in cattle.

1Deb Clopton, research technician; JorgeQuintal, Freddie Kojima, and Karol Fike, formergraduate students; Jim Kinder, professor, AnimalScience, Lincoln.

Regulation of LH Secretion byProgesterone in Heifers

of LH secretion than magnitude of shiftin amount of progesterone.

Introduction

Secretion of LH is an important com-ponent of cattle reproduction because itis necessary for the development ofovarian follicles, estradiol production,ovulation and the formation of corporalutea. Pattern of LH secretion changesduring the estrous cycle of cattle and isinfluenced by concentration of proges-terone and estradiol.

Regulation of LH secretion byprogesterone is relatively acute, aswithin 6 hours following a shift from asmall to large dose of progesterone, asignificant change in pulse frequencyof LH was observed. Understanding theendocrine mechanisms by which repro-ductive hormones, such as progester-one and LH, interact will enhancedevelopment of new management tech-niques to control estrous cycles of beefcattle.

The objective of this study was todetermine whether magnitude of shiftin progesterone or circulating amountof progesterone is more important inregulating LH secretion during the 72hours after the progesterone shift.

Materials and Methods

Seventeen post-pubertal beef heif-ers (MARC III; 1/4 Hereford, 1/4Angus, 1/4 Pinzgauer and 1/4 Red Poll)were synchronized to a common dayof estrus with two i.m. injections of


Karol FikeBrad LindseyEllen Bergfeld

Freddie KojimaJorge QuintalEraldo Zanella

Eric MelvinMichael Wehrman

James Kinder1

Release of LH is regulated moreby circulating amount of progest-erone than by the magnitude ofshift in progesterone. Understand-ing interactions of reproductivehormones advances developmentof management tools for producersto control estrous cycles of beeffemales.

Summary

Heifers experienced either a: 1)large magnitude of change in progest-erone; 2) medium magnitude of changein progesterone; or 3) small magnitudeof change in progesterone. During the24 hours following the progesteroneshift, heifers with the large magnitudeprogesterone shift had a greater LHpulse frequency than heifers with amedium or small magnitude of shift inprogesterone. Despite the large ormedium magnitude progesterone shift,LH pulse frequency did not differ fromheifers in which a small change inprogesterone occurred. We concludethat amount of progesterone in circu-lation is more important in regulation


PGF2α (25 mg Lutalyse®; The Upjohn

Co., Kalamazoo, MI) given 10 daysapart. During the eighth day of theirestrous cycle, heifers were injected witha single dose of PGF

2α to regress exist-ing corpora lutea and treatments wereinitiated (day 0). From day 0 to day 4,heifers were treated with various dosesof progesterone via

progesterone-

releasing intravaginal devices (.5 to 2PRIDs; Sanofi Animal Health Inc.,Paris, France) followed by a large doseof progesterone (2 PRIDs) from day 4.5to day 7. Change in dose of progester-one occurred on the morning of day 4,within 4 hours following collection ofthe day’s blood sample. At this time,PRIDs were removed from each heiferfollowed by immediate insertion of 2PRIDs.

Based on mean magnitude of con-centration change of progesterone incirculation from day 0 to day 4 relativeto day 4.5 to day 7, heifers were placedinto one of the following groups: 1)large magnitude of change in concen-tration of progesterone (3.1 ng/ml; n=6);2) medium magnitude of change inconcentration of progesterone (2.5 ng/ml; n=6); or 3) small change in concen-tration of progesterone (0.5 ng/ml; n=5).

Blood Collection and Radioimmuno-assays

Jugular blood samples were collectedevery 12 hours from day 0 to day 7 andused to assess circulating concentra-tions of estradiol and progesterone.Jugular blood samples were also col-lected via cannulae every 15 minutesfrom day 3.5 to day 7 to assess concen-trations of LH in circulation.

Results

Progesterone, secreted by a corpusluteum, regulated the estrous cycle incattle such that in the presence of in-creased concentrations of progesterone,pulse frequency of LH is low and estrusand ovulation are inhibited. Treatmentof beef females with doses of commer-cially used progestins (norgestomet,melengestrol acetate or progesterone)in the absence of a corpus luteum is

sufficient to inhibit ovulation. How-ever, it does not regulate pulse frequencyof LH like the greater concentrationsof progesterone present in circulationduring the luteal phase of an estrouscycle. Consequently, LH pulses are morefrequent during treatment with smalldoses of progestins than during theluteal phase of an estrous cycle. Pulsefrequency changes affect ovarian fol-licle development and their secretionof estradiol (see “Prolonged ElevatedConcentration of Estradiol Do NotAffect Conception Rates in BeefCattle” in this NE Beef Report).

Researchers have hypothesized thatmagnitude of change in progesteroneconcentration (or dose of progestin) isinvolved, along with amount of proges-terone, in regulation of pulse frequencyof LH. This hypothesis was suggestedbecause an evaluation of LH pulse pat-tern of individual animals from a previ-ous study in our laboratory indicated apossible relationship between magni-tude of shift in progesterone dose andduration of cessation of pulsatile LHsecretion.

In this study, mean magnitude ofchange in progesterone concentrationfrom day 0 to day 4 relative to day 4.5

to day 7 differed across groups (P < .02;Table 1). There were group x day inter-actions for mean concentrations ofprogesterone (P < .001; Figure 1) andestradiol (P < .01) during treatment(day 0 to day 7). Pulse frequency andmean concentration of LH differed (P <.05) across groups during the 12 hoursbefore the shift in progesterone (Table1). Pulse frequency of LH was greater(P = .05) among heifers with the largemagnitude of change in concentrationof progesterone as compared with themedium during the first 24 hours fol-lowing the shift in progesterone con-centration. Pulse frequency of LHtended to be greater (P < .10) during thefirst 24 hours following the shift inprogesterone concentration among heif-ers with the large magnitude of changeas compared with the small magnitudeof change. From 24 to 48 hours and 48to 72 hours following the shift in proges-terone concentration, pulse frequencyof LH was similar across groups. Meanconcentration of LH was similar acrossgroups during the first 24 hours andfrom 24 to 48 hours and 48 to 72 hoursfollowing the shift in progesterone.

Before the shift in dose of progester-one, there was an inverse relationship

Table 1. Mean concentration of LH, LH pulse frequency and amplitude, and mean magnitude ofchange in amount of progesterone of heifers with a large, medium, or small magnitude ofshift in amount of progesterone.

Group

Item LG MD SM

Mean magnitude of changein progesterone (ng/ml)a 3.1b 2.5c 0.5d

Mean LH (ng/ml): Pre-shift -12 to 0 hours 2.1b 1.7c 1.2d

Post-shift 0 to 24 hours 1.2b 1.2b 1.0b



LH pulses/12 h: Pre-shift -12 to 0 hours 9.7b 6.5c 3.4d

Post-shift 0 to 24 hours 5.4bx 2.8c 2.9bcy



LH pulse Pre -shift -12 to 0 hours 1.4b 1.4b 1.5b

amplitude (ng/ml): Post-shift 0 to 24 hours 0.8b 0.9b 0.8b

Post-shift 24 to 48 hours 0.6b 0.5b 1.7c

Post-shift 48 to 72 hours 0.9bx 1.5bcy 1.6c

aMean change in concentration of progesterone from day 0 to 4 relative to day 4.5 to 7 of the experiment.b,c,dMeans within a row without common superscripts differ P< .05.x,yMeans within a row without common superscripts differ P < .10.


of LH to some extent as an acute shift inamount in circulation dramaticallyaffects secretion of LH. This contraststhe gradual changes observed in releaseof LH during a typical estrous cycle,when changes in progesterone concen-tration also are relatively subtle andgradual.

Pulse amplitude of LH was similaracross groups during the 12 hours be-fore and the first 24 hours following theshift in progesterone (Table 1). From 24to 48 hours following the shift in proges-terone concentration, pulse amplitudeof LH was greater (P < .01) amongheifers experiencing a small magnitudeof change in progesterone as comparedwith heifers experiencing a large ormedium magnitude of change in pro-gesterone. From 48 to 72 hours fol-lowing the shift, pulse amplitude ofLH was greater (P < .05) among heiferswith a small magnitude of change inprogesterone concentration and tend-ed (P < .10) to be greater among heiferswith a medium magnitude of change inprogesterone as compared with heifersthat had a large magnitude of change inprogesterone. These differences in LHpulse amplitude appear to reflectsequential adjustments to the threemagnitudes of shift in progesterone.Greater amplitudes of LH pulsesresumed earlier following the shiftamong heifers with the small, followedby the medium and lastly the largemagnitude of shift in progesterone.

Results from this study indicate LHpulse frequency appears to be influ-enced more by amount of progesteronein circulation than by magnitude ofshift in progesterone. The LH pulsegenerator does not appear to be sensi-tive to different magnitudes of changein amount of progesterone.

1Karol Fike, former graduate student. BradLindsey, graduate student. Ellen Bergfeld, formergraduate student. Freddie Kojima, former graduatestudent. Jorge Quintal, former graduate student.Eraldo Zanella, graduate student. Eric Melvin,former graduate student. Michael Wehrman, formergraduate student. James Kinder, Professor of AnimalScience, Lincoln.

Figure 1. Concentrations of progesterone in circulation of heifers with a large (LG), medium(MD) or small (SM) magnitude of change in concentration of progesterone. Arrowindicates time of shift from various doses to a relatively large dose of progesterone.There was a group x day interaction (P < .01). Differences in progesterone acrossgroups within day are indicated by uncommon superscript letters (a,bP < .05; x,y P< .10).

between circulating concentration ofprogesterone and estradiol (data notshown). Heifers with lesser circulatingconcentration of progesterone and in-creased pulse frequency of LH (Table1) likely developed large dominant ova-rian follicles, resulting in the increasedconcentrations of circulating estradiol.Additionally, circulating concentra-tions of progesterone differed acrossgroups (Figure 1) before the shift inprogesterone. Differences in fre-quency of LH pulses, before the shift inprogesterone amount, can likely beattributed to differences in amount ofboth progesterone and estradiol. Pre-vious research has shown that whenboth progesterone and estradiol arepresent in circulation, a greater sup-pression of LH pulse frequency isachieved than with either steroid alone.Following the progesterone shift,however, concentration of estradiolwas similar among the three groups ofheifers. Therefore, differences in fre-quency of LH pulses following theshift may be attributed solely to pro-gesterone and not estradiol.

Heifers experiencing a large magni-

tude of change in progesterone concen-tration had less circulating progester-one and, subsequently, greater pulsefrequency of LH during the first 24hours following the shift in progester-one concentration. Apparently, the largemagnitude of shift in progesterone con-centration in these heifers did not affectpulse frequency of LH, but rather fre-quency of LH pulses during the first 72hours following the progesterone shiftwas regulated by amount of progester-one in circulation and not the magni-tude of the shift. Heifers with eithermedium or small magnitudes of shift inprogesterone had similar concentrationsof progesterone in circulation follow-ing the shift. Subsequently, frequencyof LH pulses was similar among heifersof all three groups following the proges-terone shift irregardless of the magni-tude of the shift. Based on these results,it appears that amount of progesterone,rather than magnitude of shift, is moreimportant in regulation of pulsatile se-cretion of LH during the 72 hours afterthe shift in progesterone. An acute shiftin amount of progesterone, however,appears to regulate pulsatile secretion

12

10

8

6

4

2

0

Pro

gest

eron

e (n

g/m

l)

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5 7

Day of experiment

c

a

a

aa

a

cbycb

cb

b

b

ab

bxb

b bx

byb

abxa

ax

a

by

a

ax

LG SM MD


Karol FikeMichael Wehrman

Ellen BergfeldFreddie KojimaJames Kinder1

Persistent ovarian follicles andassociated elevated concentrationsof estradiol which develop duringprogestin-based estrous synchronyprograms are not detrimental tofertility if persistent ovarian fol-licles are not allowed to ovulate.

Summary

Following treatments causing ei-ther prolonged elevated concentrationsof estradiol associated with develop-ment of persistent follicles or inhibitedelevated concentrations of estradioland development of persistent follicles,conception rates were compared. Beeffemales received either four norges-tomet implants for 9 days (day 0 =treatment initiation; n=59) or onenorgestomet implant for 7 days andthree additional norgestomet implantsfor 2 days (n=60). All implants wereremoved on day 9 followed by estrousdetection and AI for 7 days. Treatmentand day interacted to affect estradiolconcentrations from day 0 to day 9 withelevated estradiol in females treatedwith one norgestomet implant for 7days. Conception rates to AI were simi-lar across treatments. Prolonged ele-vated concentrations of estradiolassociated with development of persis-tent ovarian follicles do not affect fer-tility when persistent ovarian folliclesare not allowed to ovulate.

Introduction

Cattle treated with commercial dosesof synthetic progestins, such asmelengestrol acetate and norgestometor small doses of progesterone in theabsence of corpora lutea, often developpersistent ovarian follicles. These fol-licles develop because of greater LHpulse frequency than naturally occursduring the luteal phase which, in turn,promotes prolonged development of thedominant follicle and increased con-centrations of estradiol.

Reduced fertility is associated withestrus and mating following develop-ment and ovulation of persistent ova-rian follicles. This fertility reductionmay be due to adverse effects of pro-longed elevation of estradiol on thereproductive tract, compromised oo-cyte development in persistent ovarianfollicles or a combination of these fac-tors.

The objectives of this study were tocompare conception rates and time toestrus in cattle following treatmentsdesigned to: 1) inhibit persistent ova-rian follicle development and elevatedconcentrations of estradiol; or 2) causedevelopment of persistent ovarian fol-licles and prolonged elevated concen-trations of estradiol, but inhibit ovulationof the follicles.

Procedure

Heifers (n=80) and 2-year-oldMARC III (1/4 Angus, 1/4 Red Poll,1/4 Pinzgauer, 1/4 Hereford) cows(n=39) from the beef physiology herdwere injected twice with PGF

2α (25 mg;Lutalyse® Sterile Solution, Upjohn,Kalamazoo, MI) 11 days apart. The last

injection occurred on the day of treat-ment initiation to destroy the functionof existing corpora lutea and synchro-nize the estrous cycle stage prior toexperiment. All females exhibitingestrus were 6 to 8 days post-estrus attreatment initiation. Females were strati-fied by age, blocked by estrual status(previously exhibited estrus or anestrus)and assigned to receive either: 1) fournorgestomet implants (4 Norg; n=59;hydron implant with 6 mg norgestomet;Sanofi Animal Health Inc., OverlandPark, KS) for 9 days (day 0 = treatmentinitiation); or 2) one norgestomet im-plant from day 0 to day 7 and threeadditional norgestomet implants fromday 7 to day 9 (1+3 Norg; n=60). Allfemales received an injection of PGF

2α(25 mg) at treatment initiation and allimplants were removed on day 9.Females were observed for signs ofbehavioral estrus every 6 hours fromtime of implant removal (day 9) untilday 16 with the aid of K-Mar devicesand epididymal ligated bulls. Femalesexhibiting estrus were bred by AI 6 to12 hours following estrus detection.

Blood samples were collected dailyfrom treatment initiation (day 0) untilthe end of estrous detection and AI (day16) and twice weekly for an additional30 days thereafter. While concentra-tions of progesterone were determinedin all samples collected, concentrationsof estradiol were determined only insamples collected from day 0 to day 16.

Females were considered pregnantwhen, following breeding, concentra-tions of progesterone increased to above2 ng/ml of serum and remained at con-centrations characteristic of normalluteal function until termination of theexperiment. Uterine ultrasonography

Prolonged Elevated Concentrations of EstradiolDo Not Affect Conception Rates in Beef Cattle


approximately 35 days following AIwas to confirm the progesterone pro-files to determine if pregnancy occurredas a result of AI.

Results

There was a treatment x day interac-tion (P < .01) for concentrations ofestradiol from day 0 to day 9 of theexperiment, with elevated estradiol oc-curring in females receiving the 1+3Norg treatment (Figure 1). The increasein concentration of estradiol from day 0to day 7 in females treated with 1+3Norg was indicative of persistent ova-rian follicle development and the acutedecline in estradiol observed after treat-ment with three additional norgestometimplants was indicative of induced atre-sia of persistent follicles. Concentra-tion of progesterone in females of bothtreatment groups declined from day 0 today 1 in response to PGF

2α injected onday 0 and remained low through day 9of the experiment.

Estrous synchronization rate (num-ber in estrus/number in treatment group)and pregnancy rate (number conceivedto AI/number in treatment group) wereaffected (P < .10) by treatment x estrual

status. Estrous synchronization rate ofestrual females did not differ betweentreatment groups (Table 1). There wasa greater percentage (P < .10) of previ-ously anestrus females displaying signsof estrus within 7 days after removal ofnorgestomet implants in the 4 Norggroup (97 %) as compared with the 1+3Norg group (67 %). Age, estrual status,treatment x age and treatment x estrualstatus affected neither conception ratesnor time to onset of behavioral estrus

after removal of norgestomet implants.Conception rates (number conceived/number inseminated) to AI were notdifferent among females treated with1+3 Norg (72%) and those treated with4 Norg (67%). Pregnancy rates of bothestrual and anestrous females did notdiffer between treatment groups (Table1). Mean time from norgestomet with-drawal to behavioral estrus was longer(P < .001) in females treated with 1+3Norg (105 hours) than with femalestreated with 4 Norg (61 hours).

Using two different protocols of syn-thetic progestin treatment, elevatedconcentrations of estradiol associatedwith development of persistent ovarianfollicles were unable to affect concep-tion rate to AI. Results indicate similarconception rates can be achieved incattle in which progestin treatment al-lows a persistent ovarian follicle todevelop and subsequently causes itsregression, as compared with cattle inwhich larger doses of synthetic proges-tin treatment prohibit the developmentof persistent ovarian follicles. It ap-pears that allowing persistent ovarianfollicles and their associated elevatedconcentrations of estradiol to developis not detrimental to fertility when thefollicle is regressed before the ovula-tory follicle associated with pregnancyovulates. Conclusions drawn from thisand other studies indicate decreasedpregnancy rates observed in associa-tion with ovulation of a persistent ova-rian follicle are likely due to abnormalmaturation of the oocyte rather thaneffects of elevated concentrations ofestradiol on oviductal or uterine func-tion.

Because we induced regression ofthe persistent ovarian follicles by treat-ment with three additional norgestometimplants, we also shortened the dura-tion of elevated concentrations of estra-diol when compared with the durationin cattle ovulating persistent ovarianfollicles. In cattle receiving the 1+3Norg treatment, there was a 105 hourinterval from time of removal ofnorgestomet implants until the onset ofestrus; cows treated with 4 norgestometimplants had a 61 hour interval. It ispossible lesser concentrations of

Figure 1. Concentrations of estradiol in circulation from day 0 to 16 of the experiment offemales during treatment with either four norgestomet implants for 9 days (4 Norg) or onenorgestomet for 7 days followed by an additional three implants for 2 days (1+3 Norg).Arrows indicate day of insertion of 3 norgestomet implants in 1+3 Norg treatment groupand day of removal of all implants for both treatment groups. There is a treatment x dayinteraction (P < .01) from day 0 to 9 of the experiment.


Table 1. Estrous synchrony rates, conceptionand pregnancy rates to AI and time tobehavioral estrus of females treatedwith 1+3 Norg or 4 Norg implants

Treatment

4 Norg 1+3 Norg

Estrous synchronya (%)Estrual 97 100Anestrous 97† 67

Conception Rate (%) 67 72Pregnancy Ratea (%)

Estrual 66 77Anestrous 63 43

Time to estrus (hours) 61*** 105

†P < .10***P < .001aThere was a treatment x estrual status interaction(P < .10), therefore animals that were estrual andanestrous were analyzed separately.

18

16

14

12

10

8

6

4

2

0

17β-

Est

radi

ol, p

g/m

L

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

Day of experiment

4 Norg

1+3 Norg


Evaluation of Feather Meal forCalves Grazing Cornstalks

circulating estradiol from the time ofinduced regression of the persistent ova-rian follicle until preovulatory follicledevelopment allowed for oviductal anduterine function to return to normalbefore the oocyte/embryo entered thereproductive tract. The extended inter-val from treatment withdrawal to onsetof estrus may be due to an acute reduc-tion in LH pulse frequency resultingfrom treatment with three norgestometimplants. It is likely treatment with thethree additional norgestomet implantscaused an immediate decrease in thefrequency of LH pulses, induced atresiaof the persistent ovarian follicle anddelayed development of the next domi-nant follicle. Dominant persistent ova-rian follicles suppress development ofsubordinate follicles; therefore, it isplausible that, in females treated with1+3 Norg, subordinate follicles weresmaller resulting from the presence ofpersistent ovarian follicles and thus re-quired more time to develop to ovula-tion.

The present study provides evidencethat estrous synchrony programs basedon treatment with doses of commer-cially used synthetic progestins will notresult in compromised fertility at thesynchronized estrus if persistent ova-rian follicles are regressed before theovulatory follicle associated with preg-nancy is allowed to ovulate. Develop-ment of future estrous synchronyprograms using small doses of progestinsshould focus on allowing for ovulationof typically growing dominant folliclesor using larger doses of progestins toinhibit development of persistent ova-rian follicles.

1Karol Fike, former graduate student. MichaelWehrman, former graduate student. Ellen Bergfeld,former graduate student. Freddie Kojima, formergraduate student. James Kinder, Professor of AnimalScience, Lincoln.

D. J. JordonTerry KlopfensteinMark Klemesrud 1

Calves grazing cornstalks canbe expected to perform similarlyon either a traditional soybean mealor a sunflower/feather meal supple-ment. The sunflower/feather mealsupplement resulted in a saving of$0.05/hd/day.

Summary

Three years of cornstalk grazingtrials were conducted from 1995-97 todetermine the feeding value of a sun-flower, feather and blood meal supple-ment compared to a traditional soybeanmeal supplement. Analysis revealed noyear x treatment interaction in years 1and 2, so data were pooled. Gains ofcalves receiving soybean meal (0.97lb/day) were not significantly differentfrom those consuming sunflower/feather meal (0.83 lb/day). In year 3,protein sources were evaluated forundegradable intake protein beforeformulation. Gains were similar be-tween soybean meal (0.19 lb/day) andsunflower/feather meal (0.16 lb/day).A supplement containing sunflower/feather meal is an acceptable alterna-tive to a soybean meal supplement whilesaving approximately $50-64/ton.

Introduction

Cornstalks are an excellent source ofwinter feed for growing calves. How-ever, some type of protein supplemen-tation is required, especially toward theend of the grazing period when corngrain becomes limited. Feather meal(FM), a byproduct of the poultry indus-try, has gained significant use by cattleproducers in the past few years. Feathermeal is an excellent source ofundegradable intake protein (UIP)

allowing for maximum winter gainsbased on forage availability and qual-ity. In addition, FM is high in CP,allowing producers to deliver more totalprotein in a smaller package. WhileUIP is critical for growing calves,degradable intake protein (DIP) isequally important to maintain foragedigestion by the rumen microbial popu-lation. Sunflower meal (SM), a sourceof DIP, lends itself as a carrier in thesupplement and helps mask any pos-sible palatability problems associatedwith FM. Blood meal (BM), anothersupplement high in CP and UIP, adds anexcellent complementary amino acidprofile which has been shown to bebeneficial for young growing calves. Amixed supplement containing sun-flower, feather and blood meals shouldresult in calf gains equal to those of themore traditional, and expensive, supple-ment containing soybean meal (SBM).

The objective of this trial was toevaluate the feeding value of a sun-flower/feather meal supplement whencompared to soybean meal for weanedcalves grazing winter corn residue.

Procedure

Three consecutive years of wintercornstalk grazing trials were conductedin 1994-95, 1995-96 and 1996-97 uti-lizing 279 crossbred weaned calves. Inyear 1, 99 calves were assigned to oneof four dryland cornstalk fields in arandomized complete block design.Two fields assigned the SBM treatmentincluded 29 and 18 head, while the twoSM/FM fields contained 34 and 18 head.Head counts in each field were based onacreage and a previously determineddryland stocking rate of 1 animal/acre.In year 2, 90 calves were assigned toone of four dryland stalk fields in arandomized complete block design.Fields contained 23 and 24 head (SBM)and 28 and 15 head (SM/FM). Headcounts were determined as describedabove. In year 3, 90 calves were


assigned randomly to one of eight irri-gated stalk fields. Soybean meal fieldscontained 8, 11, 11 and 16 head whileSM/FM fields contained 8, 11, 11 and15 head. Head counts in each field werebased on acreage and an irrigated stock-ing rate of 1.2 animals/acre. Each year,half of the fields in the study received1.5 lb/hd (as-is, Table 1) of SBM supple-ment; the other half received 1.5 lb/hd(as-is, Table 1) of SM/FM supplement.

In year 3, residual corn estimationswere made in each field prior to grazingby measuring 250 x 2.5 ft strips in fourrandom locations. Whole and partialears were collected and ears were shelledand the corn weighed to determineamount of residual corn in each field inbushels/acre.

In year 1, supplements were formu-lated to contain equal amounts of CPand UIP. The same supplement formu-lations were used in year 2; however,based on calf gains in both years, CPand in situ analyses were conductedfollowing grazing in year 2 to evaluatesupplement formulations compared toactual lab values. Based on this infor-mation, the SM/FM supplement wasreformulated prior to grazing in year 3.The new formulation included 44.5%CP, 26% of which was UIP (DM basis),to more closely equalize supplementsbased on actual lab values. Prior toreformulation, both CP and in situ analy-ses were conducted on the proteinsources of each supplement. These ac-tual values for CP and UIP were used inthe new formulation. Crude protein andin situ analyses were again performed

on the mixed supplements followinggrazing.

For in situ analysis, ingredients andsupplements were incubated in quadru-plicate dacron bags, utilizing one steermaintained on a grass hay diet. Allsamples were incubated 16 hours. Afterincubation, bags were washed withwarm rinse water until water ran clear,then dried for 48 hr at 140oF, andweighed. Residue was analyzed for Nusing a nitrogen analyzer. Crude pro-tein values were determined by grind-ing ingredients and supplements andanalyzing for N.

Animal performance was measuredin terms of ADG. Both initial and finalweights were based on the average oftwo consecutive day weights followingthree days of limit feeding at 2% ofbody weight. Calves were removed fromfields when, based on visual appraisal,quantity of forage became limiting.

Results

Because analysis showed no year xtreatment interaction between years 1and 2 (1994-95 and 1995-96), data werepooled across years. Gains for calvesreceiving SBM were not different thancalves receiving SM/FM. Calves supple-mented with SBM gained 0.97 lb/d,while calves consuming SM/FM gained0.83 lb/d (Table 2). Following the analy-sis of supplements after grazing in year2, the SBM was found to be 44% CP(DM basis), 42% of which was UIP.The SM/FM was 41% CP (DM basis),33% of which was UIP. These results

may explain why SBM calves gainednumerically faster. Young calves re-quire substantial UIP for maximumgrowth. The microbial population incalves is unable to supply adequateprotein to the animal, even when maxi-mum growth is not desired. Therefore,supplying calves with increased UIPshould result in improved gains. Asindicated by the above UIP values foreach supplement, the SBM was supply-ing calves with slightly more UIP thanthe SM/FM, which likely resulted in theobserved gains. While DIP values forSM/FM would have been higher, me-tabolizable protein supplied to the ani-mal from microbial protein would likelybe limited by energy from the cornresidue. Assuming energy intake wasequal in all fields, microbial CP sup-plied to calves would have been roughlyequal in both treatments; however, basedon UIP values, metabolizable proteinwould have been slightly greater forcalves receiving SBM.

While the energy and protein inter-action is important to animal perfor-mance, energy alone can have a largeimpact on gains. An important sourceof energy for cattle on corn residue isresidual corn. Previous cornstalk graz-ing research at the University of Ne-braska has shown residual corn canhave a large impact on calf perfor-mance, with residual corn exhibiting astrong positive correlation with ADG.It is possible calves receiving SBMwere grazing in fields containing moreresidual corn; however, no residual cornestimations were determined prior tograzing in years 1 and 2.

In year 3, efforts were made toresolve supplemental protein andresidual corn questions. Formulation of


Table 2. Average daily gain of calves andresidual corn estimates by year andtreatment.

ADG, lb/hd/day

Year Soybean Sunflower/meal Feather meal

1994-1995 .59 .461995-1996 1.34 1.20Average, 1994-1996 .97 .831996-1997 .19 (.63)a .16 (.52)a

aResidual corn estimations (bu/acre, as-is).

Table 1. Supplement compositions.

Supplement, % DM

1994-96 1996-97

Ingredient SBMa SM/FMa SBMa SM/FMa

SBMa 91.4 —— 91.4 ——FMa —— 11.2 —— 18.9SMa —— 81.2 —— 69.1BMa —— 2.1 —— 2.6Urea —— —— —— 3.1Dical 3.3 1.6 3.3 2.4Vit. premix .08 .08 .08 .08Trace min. premix .26 .26 .26 .25Selenium .18 .18 .18 .18Salt 3.27 3.27 3.27 3.27Rumensin 80 .14 .14 .14 .14Pellet binder 1.36 —— 1.36 ——

aSBM = soybean meal; FM = feather meal; SM = sunflower meal; BM = blood meal.


the SM/FM supplement was revised tomore closely match the SBM supple-ment and residual corn was measuredafter harvest, but prior to animal place-ment in fields. Calf gains in year 3 weresimilar for SBM (0.19 lb/d) and SM/FM(0.16 lb/d; Table 2). Likewise, residualcorn estimates were similar with 0.63bu/acre remaining in SBM fields while0.52 bu/acre remained in SM/FM fields.

Economic analysis of both supple-ments from year 3 revealed that the SM/FM supplement was $64.40 less per tonthan SBM. This resulted in a differenceof $0.05/hd/d and a total savings of$3.87/hd over 80 days of grazing. How-ever, due to the recently inflated priceof SBM, these differences may be largerthan normal. Utilizing prices from May1996, an economic comparison for years

1 and 2 demonstrates a price differenceof $50/ton, which may be more repre-sentative of SBM costs typicallyobserved.

1D. J. Jordon, graduate student; TerryKlopfenstein, Professor; Mark Klemesrud, researchtechnician, Animal Science, Lincoln.

Feather Meal as a Source of Sulfur Amino Acidsfor Growing Steers

Mark KlemesrudTerry Klopfenstein1

Feather meal, which can pro-vide a portion of the sulfur aminoacids required by growing cattle, isan excellent source of escape pro-tein. However, additional methion-ine may further improveperformance.

Summary

One-hundred twenty individually fedsteer calves were used to evaluatefeather meal as a source of sulfur aminoacids. Treatment proteins included aurea control and meat and bone meal(6.4% of dietary DM) plus 0, 1, or 2%feather meal with incremental levels ofrumen protected methionine. Addingfeather meal to meat and bone mealresulted in a linear increase in gain.Likewise, rumen-protected methioninealso improved gain. These results indi-cate feather meal can provide a portionof the sulfur amino acids lacking inmeat and bone meal. However, addi-tional methionine may further improveperformance.

Introduction

To optimize production in growingcalves, escape protein is often supple-mented to meet the animal’s metaboliz-able protein requirement. However,

ruminants, like all animals, have re-quirements for metabolizable aminoacids rather than protein. Sources ofescape protein vary markedly in aminoacid content, ultimately affecting pro-tein utilization efficiency. Meat andbone meal (MBM), a good source ofescape protein (55% of CP), is deficientin the sulfur amino acids. Additionalmethionine in a rumen protected formimproved daily gain and protein effi-ciency in growing steers supplementedwith MBM (1995 Nebraska Beef Re-port, pp. 9-11). Feather meal (FTH) isan excellent source of escape protein(60% of CP) and sulfur amino acids.However, feather meal contributes pri-marily cysteine rather than methionine.

While methionine is an essentialamino acid, cysteine is not. Cysteineused for normal protein synthesis canbe supplied from the diet or synthesizedfrom methionine. When dietary cys-teine intake is insufficient to meet thebody’s needs, methionine is convertedto cysteine to meet this need. The re-verse reaction, however, the conver-sion of cysteine to methionine, does notoccur. Therefore, providing adequatelevels of dietary cysteine may sparemethionine from the cysteine biosyn-thetic pathway. Because of this, usingsupplements which satisfy the needs forcysteine allows expensive methioninesupplements to be used with greaterefficiency. The objective of this re-search was to evaluate FTH as a sourceof sulfur amino acids for growing cattle.

Procedure

A calf growth trial was conductedusing 120 steer calves (502 lb) indi-vidually fed diets (DM basis) of 44%sorghum silage, 44% corncobs and 12%supplement (Table 1). The steers wereassigned randomly to one of four treat-ments, which consisted of: 1) urea (con-trol); 2) MBM; 3) MBM plus 1% FTH;and 4) MBM plus 2% FTH. The level ofMBM (6.4%) was equal among thethree supplements and formulated tosupply 70 g/day of metabolizable pro-tein. The low level of FTH (1%) wasformulated to provide 30 g/day of me-tabolizable protein or 1.5 g/day of me-tabolizable sulfur amino acids. The highlevel of FTH (2%) was formulated toprovide 60 g/day of metabolizable pro-tein or 3.0 g/day of metabolizable sul-fur amino acids. Feather meal replacedurea, corncobs and tallow so all steersconsumed a diet containing 11.5% crudeprotein (DM basis).

Within each of the non-urea treat-ment proteins, steers were assigned ran-domly to amount of supplemental rumenprotected methionine. These amountswere 0, 1, 2, 3, 4 and 6 g/day. Rumenprotected methionine was supplied asSmartamine MTM (Rhône-Poulenc Ani-mal Nutrition, Atlanta, GA). All steerswere implanted with Compudose onday 1. Steers were fed individually (atan equal percentage of body weight)once daily using Calan electronic gates.Weights were collected before feedingon three consecutive days at the begin-


ning and end of the 84-day trial. Effi-ciency of sulfur amino acid utilizationwas calculated for each treatment asgain versus supplemental methionineintake, using the slope-ratio technique.

Results

Average daily gain increased ingrowing steers as metabolizable pro-tein supply increased. Steers fed theurea control supplement gained .59 lb/day; addition of MBM improved gainsto .74 lb/day (Table 2). Consistent withprevious research, supplementation ofrumen protected methionine to MBMfurther improved gains. Nonlinearanalysis predicted a maximum gain forMBM of .89 lb/day with the addition of1.5 g methionine.

Inclusion of 1% and 2% FTH toMBM improved daily gains linearly(.88 and 1.03 lb/day, respectively; Table2). The 1% FTH, which was formulated

Table 1. Diet composition (% of DM).

MBM+ MBM+Ingredient Urea MBMa 1% FTHa 2% FTHa

Base mixSorghum silage 44.00 44.00 44.00 44.00Corncobs 44.00 44.00 44.00 44.00

SupplementMeat and bone meal — 6.43 6.43 6.43Feather meal — — 1.02 2.03Soybean hulls 2.06 2.06 2.06 2.06Corncobs 4.80 1.20 .65 .10Tallow 1.40 .50 .36 .22Urea 2.16 1.22 .89 .57Sodium chloride .30 .30 .30 .30Ammonium sulfate .20 .20 .20 .20Dicalcium phosphate .99 — — —Trace mineral premix .05 .05 .05 .05Vitamin ADE premix .03 .03 .03 .03Selenium premix .01 .01 .01 .01

aMeat and bone meal, meat and bone meal plus 1% feather meal and meat and bone meal plus 2% feathermeal.

Table 2. Average daily gain of growing steers fed treatment proteins (lb/day).

Treatment Protein

Supplementalmethionine MBM+ MBM+level (g/day) Urea MBMa 1% FTHa 2% FTHa

0 .59 .74 .88 1.031 — .80 .88 1.042 — .89 .89 1.143 — .85 .92 1.074 — .90 .94 1.176 — .88 1.05 1.22SEM — .04 .04 .04

aMeat and bone meal, meat and bone meal plus 1% feather meal and meat and bone meal plus 2% feathermeal.

to supply 1.5 g of sulfur amino acids,promoted gains similar to MBM plus1.5 g rumen protected methionine. Al-though the improvement due to 1%FTH can be attributed to the additionalsulfur amino acids, the greater responseto 2% FTH may be due to a greateroverall supply of metabolizable proteinand amino acids.

The addition of rumen-protectedmethionine to the treatments contain-ing FTH also improved daily gain. Thissuggests the additional metabolizableprotein from FTH may be deficient inthe amino acid methionine, rather thantotal sulfur amino acids.

These results indicate feather mealcan provide a portion of the sulfur aminoacids not available in meat and bonemeal. However, additional methioninemay further improve performance.

1Mark Klemesrud, graduate student; TerryKlopfenstein, Professor Animal Science, Lincoln.

Cull DryEdible Beans inGrowing Calf

Rations

Ivan RushBurt Weichenthal

Brad Van Pelt1

Cull dry edible beans includeddirectly into the diets of growingcalves may decrease intake anddaily gain but improve feed effi-ciency.

Summary

Including cull dry edible beans intodiets for steer calves in two yearlytrials produced slightly different re-sults. In the first year, calculated netenergy levels were higher in diets with5 or 10% dry beans and daily gainswere equal or better than for the no-bean diets. In the second year, withequal net energy values in rations con-taining 0, 7.5 or 15% dry beans, dailygains and feed intake decreased lin-early with dry bean additions. Feedefficiency was improved as bean levelincreased.

Introduction

Dry edible beans, either great north-ern or pinto beans, are a major cash cropin western Nebraska. Cracked and dis-colored beans, which are sorted out andnot acceptable for human consump-tion, are available for animal feed. Insome years an early frost or freezestops bean growth before maturity,and although yields may be high, thebeans are unacceptable for domesticmarkets. Other environmental factors,such as bean diseases or excessive rainat harvest time, can adversely affectbean quality for human consumption.



Because of these factors, large quanti-ties of cull beans are available eachyear. Dry edible beans have 22-24%crude protein, very little fat and are arelatively good source of energy. Theycontain undesirable proteins called phy-tohemagglutinins or lectins, and if feduncooked, cause severe growth inhibi-tion to non-ruminants. Lectins appar-ently cause problems in protein digestionin the small intestine. It is unclear howmuch, if any, of the lectins are de-stroyed by the rumen microorganismsand whether or not protein digestion isaffected. It is known, however, thatwhen large quantities of dry edible beansare fed to ruminants, severe scouringwill occur.

The feed industry has used cull beansfor years in range supplements, both asa protein source and a pellet binder.Because limited data is available on thenutritive value of dry edible beans, twotrials were conducted to evaluate per-formance of steer calves fed cull dryedible beans.

Procedure

In a 1996 trial, 96 predominatelyblack Angus steers weighing approxi-mately 625 pounds each were randomlydivided into 12 pens and one of threetreatments was randomly assigned toeach pen. The three treatments were 0,5 and 10% dry edible beans. The ra-tions, as shown in Table 1, consistedprimarily of corn silage, alfalfa hay,corn and supplement. When utilizingan NEg value of 64 Mcal/cwt for drybeans, the calculated NEg of the rationswere 49.0, 51.7 and 55.1 respectivelyfor 0, 5 and 10% bean levels. At first,when the rations were balanced, theNEg level of the beans was not con-sidered and as a consequence morecorn was added to the 10% bean ration.The calculated level of crude proteinin the rations varied from 12.1% with5% dry edible beans to 12.6% forrations containing 0 and 10% drybeans. Actual bunk sample analysesrevealed that the crude protein wasslightly higher for all rations and aver-aged approximately 13% (Table 1). Allrations were supplemented with 16 g ofRumensin per ton of ration dry matter.

In a 1997 trial, 95 black steer calvesweighing approximately 572 pounds

Table 1. Rations for steer calves fed two levels of cull dry edible beans, 1996 trial.

Dry beans in diet, % of DM

0 5 10

Ingredients, % of DMCorn silage 40 47 35Alfalfa hay 26 14 11Corn 30 30 40Cull dry beans 0 5 10Additive supplementa 4.0 4.0 4.0

Calculated DM CompositionCrude protein, % 12.6 12.1 12.6UIP, % 3.9 4.0 4.3NEm, Mcal/cwt 76.4 80.3 84.3NEg Mcal/cwt 49.0 51.7 55.1Ca, % .77 .64 .58P, % .29 .30 .33

Bunk sample crude protein, % 13.9 13.5 12.6aContained 420 g of Rumensin per ton of supplement.

Table 2. Rations for steer calves fed two levels of cull dry edible beans, 1997 trial.


0 7.5 15

Ingredients, % of DMCorn silage 25.6 40.8 56.1Alfalfa hay 46.9 37.0 27.1Corn 25.7 12.9 0Cull dry beans 0 7.5 15.0Additive supplementa 1.8 1.8 1.8

Calculated DM CompositionCrude protein, % 13.0 13.0 13.0NEm, Mcal/cwt 73.9 73.6 73.2NEg, Mcal/cwt 46.0 46.0 46.0Ca, % .80 .71 .62P, % .29 .30 .32

Bunk sample crude protein, % 13.9 13.1 15.7aContained 1,200 g Rumensin per ton of supplement.

Table 3. Performance of steer calves fed two levels of cull dry edible beans, 1996 trial.


0 5 10

No. pens 4 4 4No. steers 32 32 32Initial weight, lb 622 627 624Final weight, lb 955 966 993ADG, lb 2.98a 3.03b 3.3c

DM intake, lb 20.1a 21.8b 20.0a

Feed/gain 6.73a 7.18b 6.04c

NEg/gain, MCal/lb 3.31 3.72 3.34a,b,cMeans with different superscripts on the same line are different (P < .01).

Table 4. Performance of steer calves fed two levels of cull dry edible beans, 1997 trial.


0 7.5 15

No. pens 4 4 4No. steers 31 32 32Initial weight, lb 568 573 574Final weight, lb 863 843 829ADG, lb 2.42a 2.26bc 2.15c

DM intake, lb 19.6a 17.2ac 14.8bc

Feed/gain 8.07 7.62 6.92NEg/gain, MCal/lb 3.71 3.51 3.18a,b,cMeans with different superscripts on the same line are different (P < .01).


each were randomly assigned to 12pens for three treatments: 0, 7.5 and15% dry edible beans. Rations are shownin Table 2 and were calculated to besimilar in crude protein (13%) and netenergy for gain (46 Mcal/cwt) by vary-ing the levels of corn silage, corn, al-falfa hay and dry edible beans. In thistrial, it was assumed the dry ediblebeans had an NEg value of 64 Mcal/cwt(1984 NRC). It was decided to balancethe diets to be isonitrogenous and isoca-loric. Consequently, it was necessary toalter the level of ingredients in eachration. Analyses of bunk feed samplesshowed crude protein levels similar orhigher than the calculated values.Rumensin was included at 23 g per tonof ration dry matter.

In both trials, calves were weighedin the morning before feeding on twoconsecutive days at the start and termi-nation of the trial. These weights wereaveraged to determine the starting andending weights. The trials were con-ducted for 112 and 121 days in 1996 and1997, respectively. In 1996 the calvesgrazed cornstalks with alfalfa haysupplementation before the trial; in1997, calves were fed a high roughageration between purchase and the start ofthe trial.

The source of beans was a local beanprocessor selling cull dry edible beans.They contained 24.7% crude protein,.20% calcium and .51% phosphorus (ondry matter basis). The beans were eithercracked or had discolored seed coats.

Results

In the 1996 trial, cattle receiving10% cull beans gained faster than thosefed 0 or 5% beans (Table 3). This mightbe expected, as the estimated energyconcentration of the ration was higherfor the ration containing 10% beans. Itis unclear, however, why the gain of thecattle consuming 5% beans was notdirectly between those cattle consum-ing 0 and 10% beans. One likely reason:the rations containing 0 and 5% beanscontained 30% corn, while the 10%bean ration contained 40% corn. Per-haps the additional corn provided moreutilizable energy and the 5% beans didnot provide the quantity of availableenergy the ration NEg would predict.When the quantity of net energy needed

per unit of gain was calculated, therewas no difference in the amounts re-quired in the control and 10% beanrations. The ration containing 5% beans,however, appeared to require more netenergy to produce a pound of gain. Thesteers fed 5% cull beans consumed moretotal ration than those fed either of theother diets. Feed required per pound ofgain was lowest for cattle fed 10% cullbeans and highest for the controls. Per-haps the added corn offset any objec-tionable qualities the 10% beans mayhave provided. It is not clear why thecattle fed 5% cull beans consumed morethan controls and yet when 10% beanswere fed, intake was the same as thecontrol. Also, there were no apparentdigestive problems with 10% cull beansas evaluated by feed intake and consis-tency of feces.

In 1997, as the level of beans in-creased in the ration, the gains and feedintakes decreased linearly (P < .01).Feed efficiency, however, improved aslevel of beans increased. Decrease inperformance could have been from thepossible effect of lectins on proteindestruction in the small intestine, lowerlevels of energy in beans than was as-sumed or some other attribute that de-creased the palatability of the rationscontaining beans. The levels of corn,corn silage and alfalfa also varied and itis possible that different combinationsor levels affected palatability and cattleperformance. It is questionable if thiscaused problems, however, because allof these ingredients are highly palat-able. Based on calculations of feed uti-lization, it appears the energy value ofbeans is much higher than the assumed64 Mcal/cwt. Because feed efficiencywas improved, it appears the largesteffect of the beans was related to rationintake. Perhaps cull dry edible beanscould be used as an appetite inhibitorand may be beneficial in rations wherelimit feeding is desired. The 1997 trialindicates incorporation of these beansinto growing rations results in intakeand daily gain decreases along withimproved feed efficiency.

1Ivan Rush and Burt Weichenthal, Professors,Animal Science, Brad Van Pelt, ResearchTechnician, Panhandle Research and ExtensionCenter, Scottsbluff.


ComparativeCalf Grazing of

Corn andSoybeanResidues

D. J. JordonTerry KlopfensteinMark Klemesrud 1

Soybean residues are higher incrude protein, lower in digestibleenergy and have only one-third thecarrying capacity of corn residues.

Summary

A grazing trial was conducted in thewinter of 1996-97 to compare the feed-ing value of soybean stubble to that ofcornstalks. Irrigated bean residues werestocked at 0.5 animals/acre, while irri-gated corn residues were stocked at 1.2animals/acre. Calves grazing corn-stalks gained (0.17 lb/day) faster (P =.003) than calves consuming soybeanstubble (-0.03 lb/day). In addition,calves grazing cornstalks remained infields 14 days longer. Diet sampleswere collected on both corn and soy-bean residues. Ruminally fistulatedsteer calves grazing bean stubble con-sumed diets high in crude protein (12-25%), but low in organic matterdigestibility (40-46%). Calves grazingcornstalks consumed diets from 5-6%crude protein and 60-65% digestibil-ity.


Introduction

While cornstalks are widely utilizedby cow/calf producers for winter graz-ing, many acres of bean residue areeither not utilized or utilized only as aconsequence of previously existingfence surrounding both corn and beanfields. Cattle are allowed to run on beanstubble simply because it is easier forthe producer to allow animals access toa bean field rather than fence it from anadjacent corn field. Observations sug-gest cattle spend considerable time for-aging in bean residue; however, nostudies have been conducted to deter-mine the diet quality the animals select.Although previous study has showncalves grazing corn residue gained fasterthan calves grazing a combination ofsoybean stubble and cornstalks (1997Nebraska Beef Cattle Report, pp. 26-27), it is unclear how long calves maybe wintered on solely bean residue (2acres/animal) without drastically im-pacting performance.

The objectives of the present trialwere to evaluate the feeding value ofsoybean residue compared to corn resi-due, to estimate carrying capacity ofbean residues and to determine the dietquality selected by calves grazing win-ter corn and bean residues.

Procedure

From November 22, 1996 throughJanuary 31, 1997, 123 weaned, cross-bred steer calves (540 lb) were used ina randomized complete block design tocompare the feeding value of soybeanand corn residue. Calves were assignedrandomly to one of 12 irrigated residuefields. Eight corn fields contained 16,15, 11, 11, 11, 11, 8 and 7 head. Fourbean fields contained 12, 9, 6 and 6head. Head counts in corn fields werebased on acreage and an irrigated cornresidue stocking rate of 1.2 hd/acre.Residual corn estimations were deter-mined in corn fields. Estimations weredetermined by collecting whole andpartial ears from an area 250 x 2.5 ft.Head counts in bean fields were basedon acreage and an irrigated bean resi-due stocking rate of 0.5 hd/acre, basedon the amount of available pod DM in

bean fields (1997 Nebraska Beef CattleReport, pp. 26-27).

Throughout the grazing period, calfweights from one corn field and onebean field were monitored to determinewhen the weight of cattle grazing beanresidues began deviating from cattlegrazing cornstalks. Individual weightswere taken three times weekly and plot-ted. Weights were taken using two por-table automatic scales: one set up in thecorn field; the other was placed in thebean field.

Animal performance was measuredin terms of ADG. All initial cattleweights and final weights on cattle graz-ing corn residues were based on theaverage of two consecutive day weightsfollowing three days of limit feeding at2% of body weight. Final weights forthe cattle grazing bean residues weresimply a one day weight upon removalfrom fields. Based on weights obtainedfrom the automatic scales, cattle on thebean residue were removed two weeksearlier than calves grazing cornstalks.

Diet samples were collected usingfour ruminally fistulated steer calves(525 lb). Two of the four were main-tained on a corn field; the remainingtwo calves were maintained on a beanfield. Calves were allowed a one weekadaptation to their respective fields priorto the first collection. In addition, allfour calves were supplemented with 6lb/hd (DM basis) of wet corn glutenfeed each day. Supplementation wasnecessary in order to maintain condi-tion and animal health of the calves dueto the cold conditions during ruminalevacuations. Diet samples were col-lected following complete rumen evacu-ations. Calves were allowed a 30 minutegrazing period, sampled and rumencontents replaced. While an attemptwas made to collect diet samples twiceweekly, weather often dictated whensamples were taken. Diet samples werefreeze dried, ground and analyzed forCP and IVOMD.

All calves were supplemented oncedaily with either a soybean meal or asunflower/feather meal supplement(44% CP, DM basis) at 1.5 lb/hd (DMbasis). Although this supplementationregime was another factor in the trial,no statistical differences were found

based on protein supplementation anddata were pooled across supplements.

Results

Calves grazing corn residue gainedmore weight (P = .003) than those onsoybean stubble. However, calves win-tered on soybean residue did maintaintheir initial weight over the 71 days ofgrazing and stayed healthy. Calves graz-ing cornstalks did not perform as wellas in previous years; however, this islikely a function of a lesser amount ofresidual corn remaining in fields in thewinter of 1996-1997 and a few weeks ofcold weather. Average estimates placeresidual corn grain at 4.2% of the cornyield, and yields for 1996-97 averaged138 bu/acre (as-is). In an average year,then, 5.8 bu/acre (as-is) of residual corncould be expected to remain in thefields after harvest, compared to the0.58 bu/acre (as-is) actually found in1996-97. Figure 1 illustrates a secondorder polynomial line fit to the averageweekly calf weights on both corn andsoybean residues throughout the trial.Based on the graph, it appears calvesgrazing soybean residue did not beginto deviate in weight from calves oncornstalks until the first of January.However, calves grazing corn residuecan typically be expected to gain 1 lb/d;calves in this trial gained only 0.17 lb/d. Assuming the soybean residues inthis particular year were of ‘average’quality, calf gains must not be expectedto be as similar for corn and soybeanresidues in most years as was experi-enced in the present trial.

Figure 2 shows the CP of both thecorn and soybean diets selected by calvesthroughout the trial. A treatment x timeinteraction was detected (P<.0001),because the CP values for diets selectedfrom bean residues initially declinedcompared to increases in corn residues.Differences between CP in corn andbean residues were noted from Decem-ber 14 through December 22 (P<.05) ascalves consuming bean residues werelikely consuming beans remaining onthe pods. This is supported by visualobservations of both whole beans andpods found in the diet samples. How-ever, no differences were found on


by calves consuming soybean residueswere high, IVOMD values (Figure 3)were low. Analysis of IVOMD valuesshowed a treatment x time interaction(P<.0001) as corn residues generallyincreased in IVOMD, while, in time,bean residues generally decreased inIVOMD. Corn residues were consis-tently greater (P<.05) in IVOMD com-pared to bean residues selected byfistulated steers throughout the trial.Variations in bean residue IVOMD val-ues from December 22 through Decem-ber 27 were likely due to a light snowcover.

In vitro organic matter digestibilityvalues for bean residues (Figure 3) werelower than expected. Values this lowwould not be expected to support main-tenance. Last year, IVOMD values forpods were 64% (DM basis; 1997 Ne-braska Beef Cattle Report, pp. 26-27)and whole beans were highly digested.If the calves were consuming pods andbeans early in the grazing period,IVOMD values should have been above64%. The lower values observed in thistrial may be due to consumption ofleaves and stems, which are much lowerin digestibility than pods. It is alsopossible that soybean fat was not ac-counted for in the IVOMD procedureand may have been measured as undi-gested. This would underestimate thedigestibility values for the diets, and,because the fat is higher in energy thancarbohydrates, would also underesti-mate the digestible energy content ofthe soybean residue diets.

Analysis of either corn or beanIVOMD values over time showed cornresidue diets selected by fistulated steersvaried throughout the trial, but gener-ally remained constant over the firsttwo weeks of the trial and then in-creased (from 64.6 to 67.6% IVOMD,DM basis; P<.05) from December 27-31, then remained constant until a de-crease in the last two weeks of the trial(from 70.8 to 66.8% IVOMD, DM ba-sis; P<.05). Other cornstalk grazingresearch has shown IVDMD values areroughly 60% (DM basis) after 40 daysof grazing when residual corn has beenconsumed. Calves in this trial consumedrelatively constant diets containing

Figure 3. In vitro organic matter disappearance of winter corn and soybean residues.

Figure 1. Weekly weights of calves grazing corn or soybean residues.

Figure 2. Crude protein of winter corn and soybean residues.

580

560

540

520

500

480

Wei

ght,

lb

11/22 12/12 1/1 1/21

Date

aSEM=2.81.bSEM=2.55.

CornBeans

a

b

25

20

15

10

5

0

CP

, DM

bas

is

12/14 12/24 1/3 1/13

Date

Treatment x Time interaction, P=0.0001.*Beans > Corn, P<0.05.SEM=1.29.

CornBeans


70

60

50

40

30

20

10

0

IVO

MD

, DM

ba

sis

12/14 12/19 12/24 12/29 1/3 1/8 1/13 1/18

Date

CornBeans

Treatment x Time interaction, P=0.0001.*Corn > Beans, P<0.05.SEM=1.75.

December 27, as there was a light snowcover on the ground which would haveinhibited selection of beans and pods.From that time, crude protein valueswere generally five units greater forbean residues compared to corn throughthe end of the trial.

Crude protein values increased(P<.05) initially from 4.2 to 7.3% CP

(DM basis) for calves grazing corn resi-dues. Diets from bean residues initiallydeclined (from 23.4 to 7.7% CP, DMbasis; P<.05) through December 27,then slightly increased (from 7.7 to11.1% CP, DM basis; P<.05) throughDecember 31, and remained constantthrough the end of the trial.

While the CP values of diets selected


about 60-65% digestible organic mat-ter (DM basis) and IVOMD values didnot significantly decline until the lasttwo weeks of the trial. This supportsprevious work which indicated residualcorn estimations show a significant de-cline in IVDMD values 3-4 weeks intothe grazing period, after residual cornhas been consumed. Bean residue val-ues initially declined (P<.05) from 45.7down to 31.2% IVOMD (DM basis) inthe first two weeks of the trial, thenincreased (P<.05) to 41.4% IVOMD(DM basis) from December 27-31, re-maining constant through the end of thetrial. Again, the decline in IVOMDaround December 27 was likely due tosnow cover during grazing. Without theDecember 27 collection, it is likely notime differences in terms of IVOMDwould have been found for the beanstubble.

In this particular year, while calvesgrazing bean residue did maintainweight and health at a stocking rate of 2acres/animal, still more acres (2.4) ap-pear required to carry calves as long ascalves grazing corn residue at a stock-ing rate of 0.8 acres/animal. In addi-tion, calves grazing bean residue maybe more limited by the digestible en-ergy of the residue than available resi-due, based on IVOMD values obtainedin the present trial.

The higher protein content of soy-bean residue would complement thelower protein-higher energy contentsof the corn residue when both are grazedsimultaneously. Therefore, it appearssoybean residue has some value forboth calves and cows. However, theenergy value is lower and about threetimes as many acres would be needed inorder to carry an animal on solely soy-bean residue compared to corn residue.

1D. J. Jordon, graduate student; TerryKlopfenstein, Professor; Mark Klemesrud, researchtechnician, Animal Science, Lincoln.

Solvent-Extracted Germ Mealfor Receiving Calves

Daniel HeroldMark Klemesrud

Terry KlopfensteinTodd MiltonRick Stock1

Calves fed solvent-extractedgerm meal blended with corn branand steep liquor in a receiving dietexhibited satisfactory performanceand intake.

Summary

This study evaluated solvent-extracted germ meal as a dietary ingre-dient for receiving calves. Treatmentswere 7% of dry matter as either cornbran or solvent-extracted germ meal in55% concentrate diets. Average dailygain, dry matter intake and feed to gainratio were not influenced by treatment.Dry matter offered for the first 7 dayscalves were in the feedlot also did notdiffer due to treatment. Both dry matterconsumption and calf performance in-dicated solvent-extracted germ mealcan replace up to 7% corn bran in thediet without influencing either drymatter intake or performance.

Introduction

Calves entering a feedlot are verysusceptible to respiratory diseases dueto the combined stress of weaning, ship-ping, being mixed with cattle from dif-ferent origins and adapting to a newenvironment. Good vaccination andantibiotic programs are effective in com-batting the incidence and severity ofrespiratory disease, but perhaps the most

crucial factor contributing to reducedcalf morbidity and mortality is adequatenutrition.

Unfortunately, during the first fewdays following arrival at the feedlot,calves will typically eat less than 50%of their normal feed intake and arehesitant to consume feedstuffs they areunaccustomed to. Therefore, receivingdiets for calves must be a concentratedsource of high-quality protein, digest-ible energy, vitamins and minerals toapproach meeting requirements whenintakes are low. Byproducts of the wetcorn milling industry can serve as com-ponents of receiving diets. Thesebyproducts provide both protein andenergy and also can be economical al-ternatives to corn. Corn bran and cornsteep liquor combined produce wet corngluten feed, which has been demon-strated to be an acceptable ingredient incalf receiving diets (1995 Nebraska BeefReport, pp. 28-30). Solvent-extractedgerm meal, a byproduct of corn oilproduction, has not been readily avail-able to Nebraska cattle producers. How-ever, this product could constitute anadditional energy source for ruminantdiets, either alone or blended with cornbran and(or) steep liquor. The objec-tives of this research were to determineif solvent-extracted germ meal can serveas a dietary ingredient for receivingcalves without diminishing intakes andperformance, as well as to assess ac-ceptability of this byproduct in the firstweek of feeding.

Procedure

Between October 14 and November15, 1996, 785 medium-framed steercalves (448 lb) were blocked by source


and assigned randomly to one of twodietary treatments. Treatments were 7%of the diet DM, comprised of eithersolvent-extracted germ meal (SEGM)or dry corn bran (BRAN) added to ablend of 7% steep liquor and 7% BRAN(Table 1). Therefore, corn byproductscomprised 21% of dietary DM, whichwas balanced to provide a minimum of13.5% CP, .5% Ca, .3% P, .6% K and45% roughage. Calves originated fromsale barns or were purchased directlyfrom Nebraska ranches. Loads receivedearly in the day were processed beforefeeding; those arriving late were fedgrass hay, allowed access to water andprocessed early the next day. Process-ing procedures involved vaccinationfor respiratory disease, treatment forinternal parasites, weighing, applica-tion of identification tags and alter-nately sorting animals into one of twopens as they exited the chute. A total ofnine loads of cattle were received fromdifferent sources, allowing 15 pens pertreatment.

On day 1 of the receiving trial, calveswere enticed to the bunk with one smallsquare bale of grass hay per pen, inaddition to the 6 lb DM of dietarytreatment per animal. No grass haybales were offered thereafter. However,calves were allowed to consume any

baled grass hay remaining in the bunkafter the first day. Treatment diet DM tobe fed was determined each morning toallow ad libitum access to treatmentdiets while minimizing orts. Calves wereoffered the receiving diet treatments foran average of 28 days. During the lastfour days, calves were limit-fed theirrespective treatments at an estimated2% of body weight (DM basis) to mini-mize animal weight variation due tofill, and final weights were obtained.

Throughout the receiving trial,calves were observed daily for signs ofsickness. Those showing signs of res-piratory disease or exhibiting feedingindifference were removed from theirpen and checked for elevated bodytemperature. Calves with a rectal tem-perature above 103.5oF were treatedwith long-acting antibiotic at three-dayintervals or until body temperaturereturned to normal. Animals exhibitingsigns of severe illness were pulledfrom their pen, housed where theycould be frequently observed and thetreatment diet was offered. However,intakes of ill animals did not contributeto treatment data until they werereturned to their home pen in improvedhealth, typically within three days.

Results

Calves in both treatments performedexceptionally well throughout the feed-ing period. Average daily gain forSEGM (2.60 lb) and BRAN (2.49 lb)treatments were similar (P=.22, Stderr=.06). Calves assigned to the 7%BRAN treatment consumed an averageof 13.35 lb of DM daily, which was notdifferent than 13.12 lb of DM intakeexhibited by the 7% SEGM cattle(P=.19, Std err=.12). Daily dry matterdelivered for the first week calves werein the feedlot was an indication of dietacceptability. Unlike DM intake data,DM delivery data do not account forweight of DM remaining in the bunk.Orts present at the time bunks were readwere appraised visually without beingcollected and DM offered adjusted asnecessary. For the first seven days calveswere in the feedlot, the average dailyDM delivered did not differ due to

treatment (P=.67, Std err=.21). TheSEGM treatment was delivered at anaverage rate of 7.42 lb per calf daily inthe first week of the trial; the DMdelivery associated with the BRAN dietwas 7.55 lb per calf. Similar DM deliv-ery during the first week suggests calvesaccepted both blends of byproductsequally at this dietary level. Due to anumerically higher average daily gainand lower DM intake, calves consum-ing the SEGM diet appeared to have amore favorable feed to gain ratio (5.04)than those assigned to the BRAN treat-ment (5.37). Analysis of these dataapproached significance (P=.10) sug-gesting SEGM may contain moreenergy than BRAN. This, however, isdifficult to conclude at this level ofdietary inclusion.

Calf mortality was not influenced bytreatment. Two calves from the sameload, but assigned to different treat-ments, died within four days of receiv-ing due to advanced respiratorydisease. Of calves assigned to the BRANtreatment, 49 were pulled and treateddue to elevated temperatures, whereas61 calves assigned to the SEGM dietwere likewise treated. This level of calfmorbidity resulted in 12.5 and 15.6% ofthe BRAN and SEGM calves beingtreated, respectively.

Results of this study showed thatSEGM can replace a portion of BRANin calf receiving diets without dimin-ishing performance or DM intake.Calves consumed SEGM and BRANdiets to the same extent during thecritical first week after arriving at thefeedlot and exhibited exceptional gainsand health throughout the receivingperiod. Feeding corn byproducts as aportion of the dietary concentrate inreceiving diets can diminish the needfor corn and increase use of alternativefeedstuffs not acceptable for use in theproduction of nonruminant species.

1Daniel Herold and Mark Klemesrud, researchtechnicians; Terry Klopfenstein, Professor, ToddMilton, Assistant Professor, Animal Science,Lincoln; Rick Stock, Cargill Corn Milling, Blair,NE.

Table 1. Diets used in the receiving trial(% of DM).

Treatment

Ingredient SEGMa BRANb

Dry-rolled corn 31.00 31.00Alfalfa hay 30.00 30.00Grass hay 15.00 15.00Corn steep liquor 7.00 7.00Dry corn bran 7.00 14.00Solvent-extracted

germ meal 7.00 ——Corn gluten meal 2.45 2.45Salt .30 .30Limestone .10 .10Tallow .10 .10Trace mineralsc .03 .03Vitamin premixd .02 .02

aSolvent-extracted germ meal.bDry corn bran.c10% Mg, 6% Zn, 4.5% Fe, 2% Mn, .5% Cu, .3%I, and .05% Co.d15,000 IU vitamin A, 3,000 IU vitamin D, and3.75 IU vitamin E per gram of premix.


Daniel HeroldMark Klemesrud

Terry KlopfensteinTodd MiltonRick Stock1

Solvent-extracted germ mealcan be an effective ingredient forfinishing cattle and may interactwith steep liquor/distillers solubles-corn bran blends to improve effi-ciency.

Summary

Three trials evaluated solvent-extracted germ meal for finishing ru-minants. Dry corn bran and steep liquor/distillers solubles were fed in combina-tion with solvent-extracted germ mealto evaluate interactions of byproductblends. Byproducts enhanced intakeand gain relative to dry-rolled corndiets. Adding tallow to byproduct dietsincreased efficiency. Feeding solvent-extracted germ meal with steep liquorheightened performance, but the ben-efit diminished when steep liquor levelreached 30% of dry matter. Includingsolvent-extracted germ meal with wetcorn gluten feed influenced neither dailygain nor intake. Results show solvent-extracted germ meal, either alone orblended with steep liquor/distillerssolubles and dry corn bran, is an effec-tive energy source for finishing cattle.

Introduction

The process of wet milling corn yieldsfructose or ethanol from corn starch andoil from corn germ. Byproducts of thewet milling industry include dry cornbran, steep liquor, distillers solublesand solvent-extracted germ meal. Afterthe oil is removed from corn germ,solvent-extracted germ meal may bemarketed as a component of corn gluten

feed or sold as a feed ingredient.Finishing cattle can be more effi-

cient when corn byproducts are fed incombination with dry-rolled corn com-pared with dry-rolled corn alone. Re-placing a portion of the dietary starchfrom corn with the fibrous energy ofcorn byproducts may alleviate the se-verity of subacute acidosis. However,different ratios of solvent-extractedgerm meal, dry corn bran and steepliquor may influence cattle performancedue to dietary energy content and ef-fects on intake. The objectives of thisresearch were: 1) to determine perfor-mance and intake associated with sol-vent-extracted germ meal diets withand without steep liquor/distillerssolubles; and 2) to ascertain if solvent-extracted germ meal could serve as acomponent of wet corn gluten feed whenblended with dry corn bran and steepliquor.

Procedure

Trial 1

Large framed steer calves (n=160,595 lb) were used in a finishing trialaveraging 169 days. Solvent-extractedgerm meal (GM), with and without cornsteep liquor/distillers solubles (ST), wasevaluated relative to diets containingdry-rolled corn (DRC) and wet corn

gluten feed (WCGF). Nutrient compo-sition of GM was 91% DM, 21% CP,60% NDF, .04% Ca, .33% P and .38%K. Calves were blocked by weight andrandomly assigned to one of four treat-ments. Treatments were DRC control,or either 9% GM, 19%GM+19%ST or38% WCGF replacing DRC. Final fin-ishing diets contained 92.5% concen-trate (Table 1). The WCGF used in thistrial was produced by Cargill CornMilling, Blair, NE. Calves were accli-mated to finishing diets with four adap-tation diets containing 45, 35, 25 and15% roughage, fed for 3, 7, 7 and 7days, respectively. Steers were im-planted with Revalor-S on day 1 andday 90 of the trial and fed once daily ingroups of 10 animals per pen. Dietswere formulated to contain a minimumof 11.5% CP and to meet the rumendegradable protein requirement (TDN× .081) according to 1996 NRC Nutri-ent Requirements of Beef Cattle.

Trial 2

Medium framed yearling steers(n=60, 780 lb) were used in a 118-dayfinishing trial to evaluate combinationsof GM and ST. The trial was initiated onAugust 8, 1996 when steers were re-moved from smooth bromegrass pas-tures. Yearlings were assigned randomlyto one of 10 dietary treatments, allow-

Solvent-Extracted Germ Meal, Corn Bran andSteep Liquor Blends for Finishing Steers

Table 1. Composition of diets used in Trial 1.

Diets (% of DM)a

Item DRC 9%GM 38%WCGF 19%GM,19%ST

Dry-rolled corn 83.5 74.5 50.3 50.3Ground corncobs 7.5 7.5 7.5 7.5Wet corn gluten feed — — 38.2 —Germ meal — 9.0 — 19.1Steep — — — 19.1Liquid 32b 5.0 5.0 — —Supplementc 4.0 4.0 4.0 4.0

aDRC = dry-rolled corn control, GM = solvent-extracted germ meal, WCGF = wet corn gluten feed,ST = steep liquor/distillers solubles.bMolasses, urea supplement with 50% CP (DM basis).cContains minerals, vitamins, Rumensin and Tylan in a finely ground corn carrier.


ing six animals per treatment. Treat-ments consisted of a DRC control andcombinations (% of diet DM) of either0, 15 or 30% ST blended with either 15,30 or 45% GM to replace an equalproportion of the DRC dry matter. Steerswere housed in a covered confinementfacility with southern exposure and in-dividually fed once daily using Calangates. Blends of GM and ST in ratios of50:50, 75:25, 67:33 and 60:40 (DMbasis) were mixed the day before feed-ing. This allowed the ST to permeatethe GM, simulating an equilibratedblend which had been produced at themill and transported to the feedlot. Ini-tial mixes were used as individual in-gredients in diet preparation. AdditionalST and all other ingredients within eachtreatment were individually weighedand mixed using a Data Ranger at feed-ing.

Steers were implanted with Revalor-S on day 1 of the study. Adaptation tothe high-concentrate diets was accom-plished over 21 days. Adaptation dietscontained 45, 35, 25 and 15% groundalfalfa hay (DM basis) and were fed for3, 4, 7 and 7 days, respectively. Theratios of dry-rolled corn to the ST:GMblends were maintained throughout theadaptation diets. Finishing diets con-tained 7.5% ground alfalfa hay, 25 g/ton Rumensin, 10 g/ton Tylan, traceminerals, supplemental vitamins A, D,and E and were formulated to provide atleast 12.0% CP, .7% Ca, .35% P and.6% K (DM basis).

Trial 3

Large framed steer calves (n=306,659 lb) were fed for an average of 153days to determine the performance whenfed eight different blends of ST, GMand(or) dry corn bran (BR) replacing aportion of the DRC in a 92.5% concen-trate finishing diet. Cattle were blockedby weight into one of four blocks andrandomly assigned to treatment. Twoblocks had eight steers per pen; theremaining blocks contained nine, yield-ing four pens with 34 steers per treat-ment. Calves were implanted withRevalor-S on day 1 and re-implanted onday 68. Diets were formulated to pro-vide a minimum of 12.5% CP, .7% Ca,.3% P and .6% K and contained 25 g/tonRumensin and 10 g/ton Tylan (Table2). Treatments were: 1) DRC control;2) 67%BR,33%ST; 3) 67%GM,33%ST; 4) 50%BR,50%ST; 5) 50%GM,50%ST; 6) 50%ST,25%BR,25%GM;7) 50%ST,25%BR,25%GM+fat (tallowat 3% of dietary DM); 8) 33%BR,33%GM,33%ST; and 9) 33%BR,33%GM,33%ST,+fat. Byproductblends were included to comprise 22.5%of diet DM. As in Trial 2, cattle wereadapted to grain using 45, 35, 25 and15% roughage diets. However, in Trial3 calves were fed each adaptation dietfor 7 days, and only the DRC to alfalfaratio was changed with each diet. Thedietary percentage of ST, GM and BRblends (22.5% of DM) was consistentthroughout the trial.

For initial weights in all trials, steerswere limit fed at 2% of body weight(DM basis) for 5 days to reduce filldifferences and weights were obtainedbefore feeding on two consecutive days.Final live weights were determined bydividing hot carcass weight by a com-mon estimated dressing percentage (62).Data were also collected for fat thick-ness over the twelfth rib, quality gradeyield grade, and the incidence of liverabscesses.

Results

Trial 1

Dry matter intake and ADG of cattlefed the 38%WCGF treatment werehigher (P<.05) than all other treatments(Table 3). However, there were no dif-ferences among other treatments fordaily gain or intake. Average daily gainof cattle fed the GM:ST blend wasgreater (P<.05) than that for steers con-suming GM without ST, which hadgains similar to the DRC control. Ortscollected from pens receiving the 9%GM diet appeared to have a higherproportion of GM than was present inthe initial diet. It is unclear whethersteers were actively sorting out the GMor if the dry, finely ground product wassettling in the bunk. In either case, theintegrity of the dietary balance of thistreatment was compromised with thediminished consumption of GM, which

Table 2. Diets used for finishing calves in Trial 3.

Diet (% of DM)a

50%ST 33%BR50%ST 25%BR 33%BR 33%GM

67%BR 67%GM 50%BR 50%GM 25%BR 25%GM 33%GM 33%STItem DRC 33%ST 33%ST 50%ST 50%ST 25%GM + Fat 33%ST + Fat

Dry-rolled corn 84.7 62.9 63.2 63.2 63.2 63.2 60.2 63.2 60.2Alfalfa hay 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5Dry corn bran — 15.0 — 11.25 — 5.62 5.62 7.5 7.5Steep — 7.5 7.5 11.25 11.25 11.25 11.25 7.5 7.5Germ meal — — 15.0 — 11.25 5.63 5.63 7.5 7.5Molasses 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0Tallow — — — — — — 3.0 — 3.0Supplementb 2.8 2.1 1.8 1.8 1.8 1.8 1.8 1.8 1.8

aDRC = dry-rolled corn, BR = dry corn bran, ST = steep liquor/distillers solubles, GM = solvent-extracted germ meal, Fat = tallow.bContains Vitamin A, D, and E premix, minerals, Rumensin-80 and Tylan.



could have lowered CP intake whileincreasing starch consumption.

The DRC control treatment exhib-ited a less efficient feed/gain ratio(P<.05) than treatments containingcorn byproducts. Feed-to-gain ratiofor 19%GM,19%ST (5.37) and38%WCGF (5.51) treatments didnot differ, indicating that in this trial,50:50 blends of both BR and GMwith ST had similar energy values.Feed-to-gain ratio attributed to the9% GM diet was numerically greaterthan, but not different from, the38%WGCF treatment (P=.23).

When ST and GM were combined,the GM was adhered to other dietaryingredients by the ST, diminishing theseparation potential and enhancing per-formance. Carcass quality and yieldgrades were greatest for the 38% WCGFdiets but did not differ among othertreatments.

Trial 2

Due to diet separation problems, Trial2 was designed to test for a possible GMeffect on intake, and to further investi-gate the possibility of a dietary interac-tion between GM and ST. A GM by STlevel interaction was found for bothaverage daily gain and DM intake(P<.05). Steers consuming 0 and 15%ST gained similarly across all levels ofGM (Figure 1). Gains associated withthe 30% ST treatment declined at the 30and 45% GM levels. Means for DMintake did not differ among the 15, 30,or 45% GM treatments within the 0 and15% ST levels. However, a linear de-crease in DM intake was demonstratedwithin the 30% ST treatment as level ofGM increased from 15 to 45% (P<.05)(Figure 2). An additional ST by GMlevel interaction was observed for qual-ity grade, with 30%ST,30%GM and30%ST,45%GM treatments exhibitingthe lowest values for carcass qualitygrade.

Average daily gain for DRC (3.12lb) was exceeded by the 15 (3.97 lb), 30(3.90 lb), and 45% (3.93 lb) GM levelswith the inclusion of 15% ST (P<.05).No differences were observed amongDRC and GM, ST blends at any levelfor feed conversion. No liver abscesseswere encountered in this study.

Table 3. Effect of diets on calf performance in Trial 1.

Dietsa

Item DRC 9% GM 38% WCGF 19% GM,19% ST

Daily gain, lb 3.36b 3.36b 3.90c 3.66d

DM intake, lb/day 19.72b 18.99b 21.48c 19.67b

Feed/gaine 5.88b 5.64c 5.51cd 5.37d

Quality gradef 18.47b 18.12b 18.95c 18.38b

Yield grade 2.3b 2.2b 2.8c 2.5d

Fat thickness, in .43b .43b .53c .47bc

aDRC = Dry-rolled corn control, GM = solvent-extracted germ meal, WCGF = wet corn gluten feed,ST = steep liquor/distillers solubles.b,c,dMeans within row with unlike superscript differ P<.05.eAnalyzed as gain to feed, the reciprocal of feed to gain.fHigh select = 18, low choice = 19.

Figure 2. Solvent-extracted germ meal by steep liquor/distillers solubles level interaction exhibitedfor daily DM intake in Trial 2. A linear decrease in DM intake occurred as solvent-extracted germ meal concentration increased within the 30% steep liquor level (P<.05).Mean daily DM intake for the dry-rolled corn control treatment was 23.25 lb.

Figure 1. Solvent-extracted germ meal by steep liquor/distillers solubles level interaction exhibitedfor ADG by yearlings steers in Trial 2 (P<.05). Dry-rolled corn control cattle gained anaverage of 3.12 lb per day.

Dry matter intake

26

25

24

23

22

2115 30 45

Percentage solvent-extracted germ meal

0 Steep

15% Steep

30% Steep

Average daily gain4.25

4

3.75

3.5

3.25

3

2.75

2.515 30 45

Percentage solvent-extracted germ meal

0 Steep

15% Steep

30% Steep


egories. A quadratic response was observed for DM intake as GM concen-tration moved from low to high levels(P<.01). Intake means for high, me-dium and low levels of GM were 22.5,22.1 and 23.0 lb per day. Average dailygain and feed efficiency increased lin-early for the low (3.81 lb, 6.03), me-dium (3.86 lb, 5.73) and high (3.97 lb,5.67) levels of GM (P=.01, P<.01).These responses indicated diets con-taining GM may possess more energythan those with BR. Additionally, highintake obtained with high BR diets mayhave diminished efficiency.

Results of these trials demonstratethe value of corn byproducts for finish-ing cattle relative to DRC. However,both intake and feed efficiency wereinfluenced by the composition of theBR, GM and ST blend. Consumption ofBR diets tended to be greater than whenGM was included at the same dietarylevel. Dry corn bran lacks the readilyfermentable carbohydrates present inDRC, ST and GM; it provides lowerdietary energy content while it simulta-neously diminishes the incidence ofacidosis and allows for heightened con-sumption. In Trial 2, GM alone numeri-cally enhanced performance above theDRC diet. Conversely, in Trial 1, pen-fed cattle responded to GM at 9% of dietDM with means for intake and dailygain similar to those obtained with DRC.When comparing data from Trials 1 and

Trial 3

Compared to the combined group ofcorn byproduct blends without addedtallow, the DRC treatment tended toelicit a lower average daily gain(P=.10). However, neither DM intakenor feed-to-gain ratio was different whenmeans for byproduct blends withouttallow were pooled. Combining andcontrasting treatments based on ST level(33 vs 50%) indicated a decrease in DMintake, as well as enhanced feed effi-ciency with increasing level of ST(Table 4). This analysis excluded theDRC treatment and those containing3% added tallow. No byproduct blendby tallow interaction existed, there-fore data were combined for the50%ST,25%BR, 25%GM and33%BR,33%GM,33%ST diets andcontrasted with those containing addedtallow. A significant increase in aver-age daily gain was achieved when cattleconsumed tallow (3% of DM) in addi-tion to the BR, ST, GM combinations at22.5% of dietary DM (P=.05). Feed-to-gain ratio also decreased within thesecombined treatments with tallow addi-tion (P=.06).

To examine the influence of BR andGM level on calf performance, meanswere analyzed after combining thesetwo ingredients across treatments intohigh (67 and 50%), medium (33 and25%) and low (0%) BR and/or ST cat-

Table 4. Effect of corn byproduct blends on calf performance in Trial 3.

Diet (% of DM)a

50%ST 33%BR50%ST 25%BR 33%BR 33%GM

67%BR 67%GM 50%BR 50%GM 25%BR 25%GM 33%GM 33%STItem DRC 33%ST 33%ST 50%ST 50%ST 25%GM + Fat 33%ST + Fat

Daily gain, lbb 3.74 3.80 3.95 3.82 3.99 3.86 3.92 3.85 4.02DM intake,lb/daycd 22.50 23.31 22.85 22.67 22.18 22.02 22.14 22.16 22.08Feed/gaindef 6.02 6.13 5.78 5.93 5.56 5.70 5.65 5.76 5.49Quality gradeg 18.5 18.7 18.7 18.9 18.5 18.7 18.8 18.2 18.4Yield grade 2.3 2.6 2.6 2.6 2.4 2.5 2.6 2.1 2.6Fat thickness, in .46 .50 .53 .50 .47 .51 .54 .46 .50

aDRC = dry-rolled corn, BR = dry corn bran, ST = steep liquor/distillers solubles, GM = solvent-extracted germmeal, Fat = tallow.bLinear BR vs GM level P=.01. DRC vs byproduct diets without tallow P=.10.cQuadratic BR vs GM level P<.01.d33% vs 50% ST P<.05.eLinear BR vs GM level P<.01.fAnalyzed as gain/feed, the reciprocal of feed/gain.g18 = high select, 19 = low choice.

2, it is unclear whether GM as a singleingredient provides an improvement inperformance over that exhibited by DRCalone.

When GM was combined with ST,the response in intake and daily gainwas not consistent as ST level increased.Performance of cattle in Trial 1 did notappear diminished when ST was in-cluded at 19% of DM and blended withGM. In Trial 2, however, cattle perfor-mance declined between the 15 and30% levels of ST when GM level reached30 and 45%. Feeding GM with ST atlower dietary concentration in Trial 3demonstrated a possible beneficial as-sociation between these two byproductswhen they comprise a small portion ofthe DM.

Treatments including three-waycombinations of BR, ST and GM elic-ited satisfactory intake and daily gain,indicating these three byproducts com-bined may serve as an alternative tofeeding WCGF alone. Additions of tal-low to these blends further enhancedperformance and showed tallow can becombined with corn byproduct blendsin small quantities without adverselyeffecting dietary characteristics.

1Daniel Herold, Mark Klemesrud, researchtechnicians; Terry Klopfenstein, Professor; ToddMilton, Assistant Professor; Animal Science,Lincoln; Rick Stock, Cargill Corn Milling, Blair,NE.


Lipid Sources in Finishing Diets for Yearling Steers

Ivan G. RushBurt Weichenthal

Brad Van Pelt1

Daily gain may be slightly im-proved when a corn-based finish-ing diet is supplemented with 1.12%lipid from Synergy, a processedsoybean oil refining byproduct orfrom pork fat.

Summary

Adding Synergy2 to a corn-basedfinishing diet to provide 1.12% lipiddid not significantly increase steer per-formance in this trial or in pooledresults between this trial and one re-ported in 1995. However, numericalincreases were observed in daily gainand feed dry matter intake for Synergywhen compared to control values.Pooled results for additions of pork fat(white grease) to provide 1.12 or 2.24%lipid were intermediate to those for thecontrol and Synergy treatments. Anyperformance benefit attributed to Syn-ergy may be as much from its effect ondry matter intake as it is from nutrientaddition.

Introduction

Results of a yearling finishing trialwith supplements of soybean oil refin-ing byproduct and pork fat (whitegrease) were presented in the 1995Nebraska Beef Report, pp. 22-24. Thetwo sources of lipid were equally effec-tive at improving daily gain and feedefficiency for a corn-based diet withcorn silage as the source of roughage.Sources of fat are often added to finish-ing diets to increase energy density andimprove feed efficiency. However, ani-mal fats are difficult to handle, espe-cially during cold weather, and storagetanks, piping and pumps must be heatedso the fats can be handled as a liquid.Because of the equipment investmentneeded to handle animal fats, large quan-tities need to be fed to justify the cost.As a consequence, most animal fats arefed in large commercial feedlots. Oil-seed lipids have an advantage, as theystay in a liquid state during cold weather,blending easier with liquid molassesbased protein supplements. This ad-vantage allows cattle feeders to increaseenergy density of diets by using oilseedlipids more conveniently with less ex-pensive equipment.

A second finishing trial was initiatedto study similar additions of Synergyliquid supplement or pork fat and leci-thin, a plant phospholipid, to a corn-based diet with alfalfa hay as the sourceof roughage. The objective was to de-termine effects of these lipids on dailygain, feed efficiency and carcass char-acteristics in finishing yearling steers.

Procedure

For this trial, 216 crossbred steersweighing approximately 850 lb werepurchased from one source. The steershad been fed together for the previous120 days and were uniform in condi-tion. The steers were randomly assignedto 18 pens and the pens randomly as-signed (blocked within location) to sixtreatments. The supplemental treat-ments were additions of lipids to supply1.12 or 2.24% lipid in diet dry matter asfollows:

1) Control - dry protein supple-ment (58% crude protein).

2) Combination of control andSynergy supplements to supply1.12% soy lipid from Synergy.

3) Control supplement plus 1.12%pork fat.

4) Control supplement and Syn-ergy to supply 1.12% soy lipid

Table 1. Composition of finishing diets and calculated nutrient contents.

Treatments Control Synergya Control Synergy Control Control19/14 +1.12% +1.12% +2.24% +1.12% Lecithin

Pork fat Pork fat Pork fat +1.12% Pork fat

Ingredients, % of DMCorn 83.3 78.7 81.9 77.5 80.6 80.7Alfalfa hay 10.0 10.0 10.0 10.0 10.0 10.0Beef finisher 58% 6.7 4.2 6.9 4.4 6.7 7.1Synergy 19/14 5.9 5.9Rumensin supplement 1.1 1.1Pork fat 1.12 1.12 2.24 1.12Non-medicated supp 40% 0.5Lecithin 1.12

Calculated contents, % of DMDry matter 86.8 84.6 87.0 84.7 87.1 87.2Crude protein 13 13 13 13 13 13Fat 3.9 5.0 5.0 6.1 6.0 5.7Calcium .83 .74 .85 .74 .87 .86Phosphorus .34 .38 .34 .37 .34 .34Roughage 10 10 10 10 10 10Rumensin, g/ton 30 30 30 30 30 30

aSynergy 19/14 is a patented processed product of Cargill, Inc., from soybean oil refining byproduct supplying 19% crude protein and 14% fat.


Table 3. Cattle performance and carcass characteristics with two levels of lipids and one level of lecithin.

Treatments Control Synergya Control Synergy Control Control P19/14 +1.12% +1.12% +2.24% +1.12% Lecithin Value


No. Cattle 36 36 36 36 35 36Pens/Treatments 3 3 3 3 3 3Performance

Initial wt, lb (June 7) 852 855 852 844 863 865 CoVARFinal wt, lb (Oct. 11)b 1260 1279 1267 1268 1277 1270 .58

126 day ADG, lbb 3.24 3.36 3.30 3.37 3.26 3.22 .58Feed DM intake, lb 22.8 24.0 23.0 23.2 22.6 23.0 .57Feed/gain ratio 7.05 7.15 6.98 6.94 6.94 7.16 .75

Carcass CharacteristicsHot carcass wt, lb 788 800 792 793 798 794 .58Dressing %c 62.8 63.2 63.0 63.2 63.2 63.1 .91Fat cover, in .52 .49 .54 .47 .50 .51 .86Quality graded 18.5 18.4 18.1 18.4 18.0 18.1 .48Marblinge 5.21 5.19 5.08 5.31 5.06 5.09 .81% Choice or above 68.6 66.7 54.3 62.9 60.6 55.9Rib eye area, sq in 12.7 12.8 12.6 13.1 13.1 12.3 .039Yield gradef 3.27 3.33 3.42 3.25 3.26 3.33 .45% Condemned livers 17.1 16.7 8.3 8.6 5.7 11.4

aSynergy 19/14 is a patented processed product by Cargill, Inc., from soybean oil refining byproduct supplying 19% crude protein and 14% fat.bFinal live weight adjusted by dividing carcass weight by .625, a common dressing percentage.cDressing percent = hot carcass weight ÷ full live weight x .96d Low Choice = 18, Ave. Choice = 19eSmall degree of marbling = 5, Modest = 6fYield grade evaluated by federal grader


Table 2. Average chemical analysis of diets from bunk samples.

Treatments Control Synergya Control Synergy Control Control19/14 +1.12% +1.12% +2.24% +1.12% Lecithin


Composition, % of DMDry matter 85.60 84.14 86.29 84.25 86.79 86.89Crude protein 13.87 14.13 13.37 14.10 13.82 13.93Crude fat 3.09 4.33 4.00 4.99 5.43 5.29Acid detergent fiber 8.13 7.61 7.75 7.48 8.70 7.75Calcium 0.89 0.86 0.90 0.81 0.87 0.87Phosphorus 0.36 0.38 0.36 0.38 0.36 0.39aSynergy 19/14 is a patented processed product of Cargill, Inc., from soybean oil refining byproduct supplying 19% crude protein and 14% fat.

plus 1.12% pork fat.5) Control supplement plus 2.24%

pork fat.6) Control supplement plus 1.12%

pork fat and 1.12% lecithin.

Upon arrival, cattle were processedwith routine vaccinations, pouring forexternal parasites and implanting withSynovex S. The average of two weightson consecutive days was used as theinitial weight. Individual weights weretaken both after 56 days on feed and atthe end of the trial. All weights weretaken in the early morning before feed-ing. The live weights of the cattle takenprior to slaughter were used to calculatedressing percentage; however, the finalfinished weight was based on carcassweight divided by a common dressing

percentage (.625).Final finishing diets (shown in Table

1) contained Rumensin (30 g/ton ofration DM) and Tylan (9 g/ton of rationDM). Major minerals and protein levelswere constant for all rations. The cattlewere started on rations containing 50%roughage and were stepped up by de-creasing roughage at 10% incrementsthrough three step-up rations at ap-proximately 6-day intervals. The labo-ratory analysis of bunk samplesaveraged over the feeding period isshown in Table 2.

The cattle were slaughtered after126 days on feed and liver abscess dataand hot carcass weights were collected.After a 48 hour chill, the carcasses wereevaluated for marbling, maturity, ribeye area, fat cover over the rib eye and

percentage of kidney, heart and pelvicfat. Statistical analyses were conductedutilizing SAS-GLM procedure. Themodel statement included initial weight(as a covariate), treatment, replicationand treatment by replication interac-tion. Treatment by replication interac-tion was used as the error term to test fortreatment differences.

Four treatments were common be-tween this trial and a similar one re-ported in the 1995 Nebraska BeefReport. These treatments were: con-trol; Synergy to provide 1.12% lipid;pork fat to provide 1.12% lipid; andpork fat to provide 2.24% lipid. Dietenergy levels, cattle types and days onfeed were similar. Results were pooledfor statistical analysis.


Results

Supplemental treatments did notsignificantly effect daily gain, feedefficiency or carcass characteristics(Table 3). There was a trend for cattlesupplemented with Synergy to consumeslightly more feed and gain slightlymore. Feed efficiency did not appear tobe different among the treatments.Ration quality (absence of dust or fines)appeared to be higher for the rationscontaining Synergy and lowest forthe control ration. When lecithin wasadded at 1.12% of the ration DM alongwith 1.12% pork fat, dry matter intakeand steer performance were similar tothose observed in the control steers.

Carcass dressing percent, fat cover,marbling, quality grade and yield gradewere not affected by treatments. Per-centage of condemned livers was notincreased by lipid treatments over thecontrol.

Four steers were removed from theoverall analysis. One steer died unre-lated to the treatment. Two other steerswere more than two standard deviationsbelow the average for daily gain andanother steer experienced health

problems and had sub-standard gains.As a consequence, one steer wasremoved from the control treatment,one from Synergy plus 1.12% pork fattreatment, one from control plus 2.24%pork fat treatment and one from the1.12% pork fat plus 1.12% lecithin treat-ment.

Pooled results for the four treatmentscommon between this trial and the simi-lar 1995 trial are presented in Table 4.Non-significant increases in daily gainand feed dry matter intake are shownfor Synergy over the control values.The 1.12% lipid addition to the dietfrom Synergy may not affect perfor-mance as much as it affects dry matterintake. The easy-flowing Synergy liquid

Table 4. Pooled results for two finishing trials with Synergy and pork fat supplements.

Control Synergy Pork fat Pork fat P1.12% lipid 1.12% lipid 2.24% lipid Value

No. of pens 6 6 6 6No. of steers 71 71 71 71Initial wt, lb 822 823 821 825Final wt, lba 1240 1264 1255 1255 .35Daily gain, lba 3.33 3.52 3.46 3.42 .35Feed DM intake, lb 23.6 24.6 24.1 23.8 .47Feed/gain ratio 6.30 6.32 6.24 6.28 .63

aFinal live weight and daily gain calculated by dividing hot carcass weight by a common dressingpercentage (62.5).

supplement appeared to improve rationquality by reducing fines or dust, whichcould be the reason for any increasedfeed intake. These results suggest lipidfrom soybean oil refining byproduct isas effective as pork fat (white grease)for supporting performance of finish-ing steers.

1Ivan Rush and Burt Weichenthal, Professors,Animal Science; Brad Van Pelt, ResearchTechnician, Panhandle Research and ExtensionCenter, Scottsbluff.

2Synergy 19/14 supplement is a patentedproduct of Cargill Molasses Liquid ProductsDivision, Elk River, MN, and supplies 19% crudeprotein and 14% lipid from processed soybean oilrefining byproduct.

An Enzyme-Microbial Feed Productfor Finishing Steers

Burt WeichenthalIvan Rush

Brad Van Pelt1

The MSE feed additive contain-ing multiple enzymes, microbesand yeast appears to be competi-tive with Rumensin/Tylan for sup-porting an economical finishingperformance in yearling steers.

Summary

Feeding MSE (multiple stabilizedenzymes in an enzyme-microbial feedproduct) at the rate of 2 lb of productper ton of diet dry matter in two trials

with finishing yearling steers, increaseddaily gain by an average of 6.9% overfeeding Rumensin-Tylan at 29 g and 10g per ton, respectively. Feed-to-gainratio was improved by an average of5.6% with MSE in the same compari-son. Carcass measurements were simi-lar, except for slight increases in hotcarcass weight and dressing percentfor cattle fed MSE. Percentages of liverabscesses were low and similar forboth treatments.

Introduction

The 1996 Nebraska Beef Report (pp.68-69) included results from a finishingtrial using British crossbred yearlingsteers in which Rumensin-Tylan was

compared to MSE, a feed product con-taining multiple stabilized enzymes plusfour strains of bacteria (three Lactoba-cillus cultures and one of Bacillussubtilis), three strains of yeast (Saccha-romyces cerevisiae) and three strains offungi (two of Aspergillus oryzae andone of Aspergillus niger). Steers fedMSE gained about 10% faster and 7.5%more efficiently than those fedRumensin-Tylan. Liver abscesses weresimilar for both treatments. These re-sults suggested Rumensin-Tylan couldbe replaced by MSE, especially in situ-ations such as organic beef production,without the use of antibiotics. A secondtrial was initiated to test the same com-parison with large-framed yearlingsteers and a similar diet differing only


in the replacement of 35% of the corndry matter with ground, ensiled high-moisture corn.

Procedure

Charolais crossbred yearling steerswere purchased in the spring for allot-ment to 12 pens of nine head each forsix pens on each of two treatments: (1)Rumensin fed at 29 grams and Tylan at10 grams per ton of diet dry matter, and(2) the enzyme-microbial feed productMSE fed at 2 lbs per ton of diet drymatter. Three step-up diets were used toreach the final diet, which on a drymatter basis included 53.6% dry rolledcorn, 28.9% high-moisture corn, 10.0%corn silage and 7.5% protein-mineral-vitamin supplement including NPN andnatural protein to provide 58% crudeprotein. Calculated nutrient contents ofthe diet dry matter were 12.5% crudeprotein, .65 Mcal NEg per lb, .77%calcium and .34% phosphorus.

The MSE was premixed at the rate of2 lbs of MSE with 8 lbs of finely groundcorn so that ten pounds of premix wereadded to the mixer truck after all otheringredients had been added. During thefirst 72 hours on feed, MSE was fed at6 lbs of diet dry matter (three timeshigher than the long-term feeding rate).Rumensin was fed at 25 grams per tonof diet dry matter during the first threedays, at 28 grams during the next step-up and at 29 grams thereafter. A pelletedprotein supplement with and withoutRumensin-Tylan was used in the study.

The large-framed, yearling Charo-lais crossbred steers, weighing about812 pounds when started on trial onFebruary 22, 1996, were purchasedfrom two sources and were notimplanted. The steers were fed once aday at levels allowing them to clean upmost of the feed before the next feed-ing. The steers were slaughtered after139 days on feed and carcasses wereevaluated for dressing percentage, fatthickness, marbling, quality grade, ribeye area and yield grade.

One steer died during the test, appar-ently unrelated to treatment, and onebull was removed. Carcass measure-ments could not be taken on a fewcarcasses per treatment at the packing

Means for carcass measurementswere similar between treatments. Nu-merical differences in hot carcassweight, dressing percent, marbling scoreand yield grade, were not statisticallysignificant. Rib eye area was larger (P <.06) with MSE, but rib eye area per cwtof carcass was the same. Percentages ofliver abscesses were 13.2 and 11.3% forRumensin-Tylan and MSE, respec-tively, which were neither excessivenor unusual for a high-grain diet inwhich the only roughage componentwas in the corn silage fed at 10% of dietdry matter.

Since the 1995 and 1996 trials weresimilar in design, and there were nointeractions between years, results werepooled (Table 2) for statistical analysis.Pooled means for 12 pens on each treat-ment resulted in improvements for MSE(P < .1) in final weight (adjusted to acommon 62% carcass dress), hot car-cass weight, daily gain and feed conver-sion. Dressing percent was higher forMSE (P < .05). Feeding MSE at the rateof 2 lb of product per ton of diet drymatter increased daily gain by an aver-age of 6.9% over the feeding ofRumensin-Tylan at 29 g and 10 g perton, respectively. Feed-to-gain ratio was

Table 1. Rumensin-Tylan vs MSEa for large-framed finishing steers, 1996 trial.

Rumensin-Tylan MSE

No. of pens 6 6No. of steers 51 51Initial weight, lb 810 814Daily gain, 84d, lb 4.04 4.19Final weight, lbb 1284 1305Daily gain, 139d, lbb 3.41 3.54Feed DM intake, lb 21.82 21.91Feed/gain 6.41 6.19Hot carcass weight, lb 796 809Dressing percent 63.6 64.0Fat thickness, in .31 .29Rib eye area, sq in 14.3c 14.6d

Rib eye area, sq in per cwt of carcass 1.8 1.8Marbling scoree 5.1 5.0Quality gradef 18.2 18.0Percent Choice 51.0 45.3Yield grade 2.1 1.9Liver abscesses, % 13.2 11.3

aMSE = Multiple Stabilized Enzymes, an enzyme-microbial feed product of Natur’s Way, Inc., Horton,KS.bFinal weight and daily gain were calculated by dividing hot carcass weight by a common dressing % (62).cdMeans differ (P < .06).eMarbling scores: Small begins at 5.0, Modest at 6.0.fQuality grade scores: Choice- begins at 18.0.

plant, but hot carcass weights wereavailable on 51 carcasses per treatmentand measurements for fat thickness andrib eye area were available for 48 car-casses per treatment. Final weights anddaily gains were calculated for 51 steersper treatment by dividing hot carcassweights by a common dressing percent(62). Daily gains and carcass measure-ments for individual steers were ana-lyzed by the general linear model inSAS. Feed intake and feed conversionmeans were analyzed by SAS with penas the experimental unit.

Results

Average daily gains for Rumensin-Tylan and MSE treatments were 4.04and 4.19 lb at 84 days, and 3.41 and 3.54lb (P = .42) at 139 days on feed, respec-tively (Table 1). Means for dry matterintake were similar for both treatments.At 84 days, a power outage during hotweather caused the cattle to be withoutwater, which reduced feed intake. How-ever, both treatment groups came backon full feed in a few days. Final feed togain ratios were 6.41 and 6.19 forRumensin-Tylan and MSE, respec-tively, a difference not statistically sig-nificant (P = .24). (Continued on next page)


Table 2. Rumensin-Tylan vs MSEa for finishing yearling steers, 1995 and 1996 trials pooled.

Rumensin-Tylan MSE

No. of pens 12 12No. of steers 96 94Initial weight, lb 835 838Final weight, lbb 1267 1298Daily gain, 130 d, lbb 3.32c 3.55d

Feed DM intake, lb 22.36 22.62Feed/gain ratio 6.77c 6.39d

Hot carcass weight, lb 785c 805d

Dressing percent 63.1e 63.7f

Fat thickness, in .42 .41Rib eye area, sq in 13.6e 13.9f

Rib eye area, sq in per cwt of carcass 1.7 1.7Marbling scoreg 5.3 5.2Quality gradeh 18.5 18.3Percent Choice 63.6 58.3Yield grade 2.5 2.4

aMSE = Multiple Stabilized Enzymes, an enzyme-microbial feed product of Natur’s Way, Inc., Horton,KS.bFinal weight and daily gain were calculated by dividing hot carcass weight by a common dressing % (62).cdMeans differ (P < .1).efMeans differ (P < .05).gMarbling scores: Small begins at 5.0, Modest at 6.0.hQuality grade scores: Choice- begins at 18.0.

improved by an average of 5.6% whenMSE was fed. Carcass measurementswere similar except for increases in hotcarcass weight (P < .1) and dressingpercent (P < .05) with MSE. Althoughthe mechanism for any response to MSEremains to be defined, improved feedutilization is suggested during ruminaldigestion. The costs of the two feedadditive treatments were similar, so thefeeding of MSE appears to be com-petitive with the feeding of Rumensin-Tylan to finishing yearling steers.These results may also be useful forproducers of organic beef wherethe routine feeding of antibiotics isavoided.

1Burt Weichenthal and Ivan Rush, Professors,Animal Science; Brad Van Pelt, research technician,Panhandle Research and Extension Center,Scottsbluff.

Lime Filtrate as a Calcium Sourcefor Finishing Cattle

Mark KlemesrudTerry Klopfenstein

Todd Milton 1

Lime filtrate can effectivelyreplace limestone as a source ofcalcium in beef finishing diets.However, inclusion of excess cal-cium may depress animal perfor-mance.

Summary

Finishing diets containing wet corngluten feed were fed to 128 yearlingsteers to evaluate inclusion of limefiltrate as the source of supplementalcalcium. Lime filtrate supplied 0, 50,100 and 150% of the base calcium levelof .70%, with limestone supplying theremainder. While dry matter intake

was reduced for the 100% level ofcalcium from lime filtrate (P<.10),average daily gain and feed efficiencywere not different from the limestonecontrol. The 150% level of calciumfrom lime filtrate did reduce averagedaily gain and feed efficiency (P<.10).

Introduction

The wet milling industry producesbyproducts primarily used in livestockfeeding operations and feed manufac-turing. Steep liquor and distillerssolubles are added to corn bran to manu-facture wet corn gluten feed. Althoughwet gluten feed is high (.5 to .8%) inphosphorus, it is very low in calcium.Supplemental calcium, usually in theform of limestone, must be added tocattle diets including wet gluten feed toensure adequate amounts of dietarycalcium.

The corn milling process, on theother hand, utilizes large quantities ofwater treated with hydrated lime. Thishigh-calcium residual lime filtrate iscurrently disposed of in landfills orapplied to fields for pH adjustment.Addition of lime filtrate to wet corngluten feed may replace limestone asthe source of supplemental calcium infinishing diets.

The objectives of this trial were toevaluate lime filtrate as a calcium sourcefor cattle finished on wet corn glutenfeed and to determine the optimal in-clusion level of lime filtrate in cattlefinishing diets.

Procedure

A finishing trial was conducted us-ing 128 yearling crossbred steers (850lb) to evaluate lime filtrate as a sourceof calcium relative to limestone. Steers


were blocked by weight into four repli-cations and assigned randomly, withina block, to one of four pens (8 head/pen). Each pen within a block wasassigned randomly to one of four di-etary treatments based upon the inclu-sion level of lime filtrate. Lime filtratesupplied 0, 50, 100 and 150% of thedietary calcium level of .70%, withlimestone supplying the remainder(Table 1). Although the dietary calciumrequirement was .36% (850 lb steergaining 3.4 lb/day at 26 lb DMI; 1996Nutrient Requirements for Beef CattleComputer Model), the .70% calciumlevel was used to maintain acalcium:phosphorus ratio greater than1.2. Previous research has shown im-proved feed efficiency when .70% cal-cium was fed.

The dietary phosphorus content,.53%, was greater than the requirementof .18% (850 lb steer gaining 3.4 lb/day

Results

Two replications of steers were fedfor 116 days; the remaining two repli-cations were fed for 129 days. Inclusionof lime filtrate to supply 100% of thesupplemental calcium reduced dry mat-ter intake relative to limestone (P<.10).This did not appear to be a problemassociated with palatability since in-take was not significantly reduced forthe 150% level of calcium from limefiltrate. More importantly, the 50 and100% levels of calcium from lime fil-trate were not detrimental to averagedaily gain or feed efficiency (Table 2).Actually, a numerical improvement infeed efficiency occurred when lime fil-trate was the sole source of additionalcalcium.

Feeding lime filtrate to provide morethan .70% calcium was detrimental;animal gains tended to be reduced whenlime filtrate was fed to supply 150% ofthe .70% calcium level. Likewise, the150% level of calcium from lime fil-trate significantly reduced efficiency(P<.10). Quality grade was also signifi-cantly reduced when the 150% levelwas fed (P<.10). This difference in qual-ity grade may be due to the numericaldifference in final weight and averagedaily gain. Backfat thickness, measuredbetween the 12th and 13th rib, wassignificantly reduced when the 100%and 150% levels of calcium from limefiltrate were fed (P<.10), although levelof calcium from lime filtrate did noteffect yield grade.

Lime filtrate appears to be equal tolimestone as a calcium source for fin-ishing cattle, as it supported animalperformance equivalent to limestonewhen fed to replace 50% and 100% ofthe supplemental calcium. However,inclusion of lime filtrate in excess of the.70% calcium level depressed animalperformance. This is consistent withprevious research.

1Mark Klemesrud, graduate student; TerryKlopfenstein, Professor, Todd Milton, AssistantProfessor, Animal Science, Lincoln.

Table 1. Lime filtrate as a calcium source, ration composition

% Supplemental Ca from lime filtrate

Ingredient, % diet DM 0 50 100 150

Corn gluten feed 45.00 45.00 45.00 45.00Dry rolled corn 43.07 43.00 42.95 41.95Alfalfa hay 7.50 7.50 7.50 7.50Supplementa 3.00 3.00 3.00 3.00Limestone 1.43 .72 — —Lime filtrate — .78 1.55 2.55

% Dietary Ca .70 .70 .70 1.05

aContains corn, salt, tallow, trace minerals, vitamins, Rumensin and Tylan.

Table 2. Animal performance response to inclusion of lime filtrate.

% Supplemental Ca from lime filtrate

Item 0 50 100 150 SE

Initial weight, lbs 849 850 852 852 1.7Final weighta, lbs 1268 1259 1264 1245 12.5Average daily gain, lbs 3.41 3.33 3.37 3.19 .10Dry matter intake, lbs 26.75b 25.93bc 25.51c 25.70bc .47Feed/gaind 7.81bc 7.75bc 7.58b 8.06c .21Backfat thickness, in. .55b .54b .48c .47c .02Quality gradee 19.28b 19.25b 19.00bc 18.88c .12Yield grade 2.66 2.53 2.53 2.59 .12

aHot carcass weight divided by a common dressing percentage (62%).b,cValues within a row with unlike superscripts differ (P<.10).dFeed/gain analyzed as gain/feed. Feed/gain is the reciprocal of gain/feed.eQuality grade of 20=average Choice, 19=low Choice, 18=high Select.

at 26 lb DMI; 1996 Nutrient Require-ments for Beef Cattle Computer Model)due to the high level of phosphorus inwet corn gluten feed. Diets were formu-lated to contain a minimum of 12%crude protein, 6.8% degradable pro-tein, .6% K, 25 g/ton Rumensin and 10g/ton Tylan. Steers were implanted withRevalor-S at the initiation of the experi-ment. Initial weights were the averageof weights collected on two consecu-tive days (October 14th and 15th, 1996)following a four-day period of limitedintake to reduce weight variation due tofill. Final weights were calculated fol-lowing slaughter by dividing hot car-cass weight by 62% (common dressingpercentage). Average daily gain, drymatter intake and feed/gain were per-formance criteria evaluated. Addition-ally, carcass criteria evaluated includedfat thickness at the 12th rib, qualitygrade and yield grade.


Extended Grazing and Byproduct Diets in BeefGrowing Finishing Systems

utilized by monogastrics. Our objec-tives in this study were to minimizecosts of beef production by increasingforage gains and optimizing byproductdiets.

Procedure

Experiment 1.

Sixty-three cross-bred lambs wererandomly assigned to one of seven treat-ments according to a 2 × 3 + 1 factorialdesign (Table 1). There were twobyproduct diets: one, a wet corn glutenfeed which is a blend of 1/3 steepliquor/distiller solubles and 2/3 cornbran; and the second diet, where one-half of the corn bran was replacedwith wheat midds. Steep liquor/distillersolubles remained constant across alldiets. Tallow was added to each of thebyproduct diets at concentrations of 0,4 and 8% replacing either bran or branand midds. Corn gluten meal and bloodmeal were added to the byproduct dietsto supply equal undegradable intakeprotein to the dry rolled control. Thelambs were individually fed for 84 days.They were “stepped up” by feeding 2%of body weight initially and increasingintake by .2% body weight each dayuntil ad libitum intake was achieved.Lambs were weighed three times at the

initiation and conclusion of the trial.Economic analyses used prices fromFeedstuffs magazine for wheat middsfrom July 18, 1994 to November 6,1995 which averaged 67% the price ofcorn grain. Other prices used were ac-tual market prices.

Experiment 2.

One-hundred-twenty eight British-breed steer calves were wintered oncornstalks and hay. On May 5, 1996,they were randomly allotted to 16 groupsand eight treatments (Table 2). Thecalves averaged 579 lb on May 5 whenthey were implanted with Compudose,fly tagged and placed on pasture. Thecattle were fed a common diet at 2% ofbody weight five days before beingweighed on two consecutive days at thebeginning and the end of the grazingperiods. On June 13,1996, cattle fromthe two treatments were moved to warm-season grass and returned to brome onAugust 23, 1996.

For fall grazing, the appropriate cattlewere moved to oats on September 18,1996 and returned to brome on October22, 1996. The oats had been seeded inwheat stubble. The appropriate cattlewere moved to cornstalks on Septem-ber 30, 1996. The cornstalks were avail-able at that time because the grain had

Ramiro LucenaTerry KlopfensteinMark Klemesrud

Rob Cooper1

Maximizing amount of gain onforages reduced costs of produc-tion and slaughter breakevens ingrowing-finishing beef systems.

Summary

Two experiments evaluated meth-ods of reducing costs of finishedbeef. The first experiment, usedlambs as a model for cattle. A dryrolled corn diet served as a controland two byproduct diets: 1) corngluten feed; or 2) gluten feed pluswheat midds, were supplementedwith three levels of tallow. Byproductdiets gave feed efficiencies nearlyequal to corn and efficienciesincreased with tallow supplementa-tion . In the second experiment, 128steers were used in grazing systemsincluding smooth brome, warm-seasongrasses, oats and cornstalks andfinished on corn or byproduct diets.High forage gains reduced costsand slaughter breakevens.

Introduction

Forages are an important part of beefproduction but often are not used to thebest extent. We have found (1995 BeefCattle Report, pp 34) maximizing theamount of gain on forage before enter-ing the feedlot reduces costs of pro-duction. There are, however, a numberof alternative ways to achieve maxi-mum gain including high rates of for-age gains and longer time periods onforage.

For one, cattle can be finished onbyproducts (1995 Beef cattle Report,pp 34). Byproducts are generally pricedcheaper than corn and are not well

Table 1. Diet composition as a % of DM.

1 2 3 4 5 6 7

Dry rolled corn 87.5Corn bran 60.71 56.66 52.66 30.02 28.01 26.02Wheat midds 29.36 27.40 25.44Steep liquor 29.11 29.12 29.12 29.27 29.26 29.26Alfalfa hay 5.01 5.09 5.09 5.08 5.11 5.12 5.11Liquid 32 3.75Control supplementa 3.81Treatment supplementb 3.89 3.89 3.89 3.91 3.91 3.90Fat (tallow) 4.05 8.06 4.06 8.10Limestone 1.20 1.19 1.19 2.32 2.24 2.16

aControl supplement: fine ground corn (54.95%), limestone (24.09%), salt (7.26%), potassium chloride(6.56%), ammonium Sulfate (6.05%), sheep trace minerals(.73%) and vitamins (.36%).bTreatment supplement: corn gluten meal (72.36%), blood meal (13.42%), salt (7.17%), ammoniumsulfate (5.97%), sheep trace mineral(.72%) and vitamins (.36%).


When compared to DRC, feed costswere reduced when byproducts wereincluded, however, fat addition in-creased costs. Costs of gain were re-duced by byproduct feeding.

Experiment 2.

Treatment combinations and graz-ing days are shown in Table 2. Summerrates of gain were typical for smoothbrome (1.30 lb/day; Table 4). Rotationof cattle to warm-season grasses im-proved gain to 1.97 lb/day (P<.01). Fallgrazing was a combination of bromeregrowth and oats or cornstalks. Earlyremoval steers, which grazed onlybrome in the summer, averaged 1.86lb/day gain in the fall. Those also onwarm-season grass in the summer gained1.28 lb/day in the fall.

Early removal cattle gained 1.97lb/day when grazing oats and brome,versus 1.36 lb/day for those grazingcornstalks and brome (P<.01). Whileforage quality and cattle performancewere excellent for the oats, carryingcapacity was poor . Cornstalks did notprovide previously obtained animalperformance (1996 Nebraska BeefReport, pp 48-51 and 1997 NebraskaBeef Report, pp 56-59). Cornstalkquality is variable and heavily influ-enced by the amount of dropped ears.While harvesting corn early for high-moisture corn provides earlier grazing,it is likely there is less corn on theground available for cattle.

Cattle grazing oats in the fall andgaining more weight than those on corn-stalks also gained more weight in thefeedlot (3.04 vs 2.66) and had betterfeed conversion (9.11 vs 10.83). Theextra weight gained in the fall wasmaintained and actually enhanced feed-lot performance.

Cattle fed the byproduct diet gainedless (2.78 vs 3.51 lb/day) and had poorerfeed conversions (10.34 vs 7.95; Table4) than cattle fed the DRC diet. It isunclear why the cattle performed pooreron the byproduct diet when the lambsperformed equally well on byproductsversus DRC.

Carcass data were similar acrosstreatments. Cattle had .32 to .44 inches

Table 2. Treatment description and days in summer, fall and finishing phases.

Item Treatment: 1 2 3 4 5 6 7 8

SummerBromegrass 130a 130 59 59 130 130 130 130Warm seasonb 71 71

FallBromegrass 18 47 18 47 18 47 18 18Oats 35 35 35Cornstalks 64 64 64 105 105

FinishingDry rolled cornc 94 94 86All byproductsd 94 94 94 94 86

aDays allowed to forage or finishing dietbComposed of the following species: big bluestem (Andropogon gerardii), indian grass (Sorghastrumnnutans), sideoats grama (Bouteloua curtipendula), little bluestem (Schizachyrium scoparium) andswitchgrass (Panicum virgatum).cDry-rolled corn 85.46%, alfalfa 7.5%, molasses 5.6% and 1.98% supplement (dry-rolled corn .52%,limestone 1.40%, salt .3%, tallow .1%, potassium chloride .146%, Rumensin .0165%, and Tylan .011%)dWet corn gluten feed 60%, wheat midds 30%, alfalfa 7.5% and 2.5% supplement (dry-rolled corn .67%,limestone 1.35%, salt .3%, tallow .1%, beef trace mineral .02%, Rumensin .0165%, Tylan .011%, vitaminpremix .01%, cuO .007% and thiamin 006%).

Table 3. Lamb performance and economical analyses by treatment.

Treatment Gain/ Feed/ Cost/ Cost/ADGab DMIb Feed Gain 100 lb feed 100 lb gain

Dry rolled corn 0.48 2.44 0.19 5.15 $6.45 $33.24Corn branc, 0 %fat 0.48 2.88 0.17 5.92 5.43 32.12Corn bran, 4 %fat 0.64 3.04 0.21 4.73 5.93 28.02Corn bran, 8%fat 0.62 2.68 0.23 4.41 6.43 28.37Wheat middsc, 0 % fat 0.57 2.97 0.19 5.30 5.04 26.70Wheat midds, 4 % fat 0.59 2.97 0.20 4.94 5.57 27.57Wheat midds, 8 % fat 0.64 2.84 0.22 4.53 6.10 27.66

aLinear effect for fat addition (P<.10).bQuadratic effect for fat addition (P<.10)cNo substitution effect among byproducts (P>.05).


been harvested and stored as high-moisture grain. On December 3, 1996,the early removal treatments weremoved to the feedlot for finishing. Late-removal cattle were moved to freshcornstalks for grazing until January 13,1997. Cattle were finished on a dryrolled corn (DRC) diet or a byproductdiet (Table 2). All cattle were implantedwith Revalor S upon entry in the feed-lot. The early removal cattle were fedfor 94 days; the late removal for 86days. Carcass weights at slaughter di-vided by .62 (common dressing per-centage) were used as final weights.Yield and quality grades, fat thickness,percentage choice and ribeye area wereobtained at the slaughter plant.

Results

Experiment 1.

Lambs on the byproducts diets with-out added fat gained as rapidly as didthose on DRC (Table 3). Fat content ofthe DRC diet was slightly higher thanthe byproduct diets. With 8% fat addi-tions, byproduct diets had total fat con-tents of 12 to 12.6%. Dry matter intakeswere higher on the byproduct diets thanon the DRC diet. Feed conversion wasslightly poorer for the byproduct dietswithout fat than for the DRC diet. Fataddition linearly increased gains (P<.10)and decreased feed conversions (P<.05).Corn bran and wheat midds had equalfeeding values.


Table 4. Total performance for steers in different growing-finishing combinations.

Removal: Early (12/1/96) Late (1/13/97)

BGa BG BG-WS BG-WS BG BG BG BGCS OATS CS OATS CS OATS CS CS

DRC DRC BYP BYP BYP BYP DRC BYPItem 1 2 3 4 5 6 7 8

Weight, lbMay 5 576 579 578 578 579 579 578 581Sept. 12 750 758 830 837 731 749 758 737Dec. 1 876 934 898 979 873 916Jan. 13 917 905Final 1173bf 1258c 1129e 1236cd 1094e 1193bd 1255c 1203bd

Daily Gain, lbSummer 1.33bc 1.39c 1.94d 2.00d 1.17b 1.31bc 1.38bc 1.20bc

Fall 1.53bc 2.15d 0.83f 1.73c 1.72c 2.04d 1.30e 1.37bc

Total 1.43b 1.77ce 1.39bd 1.86e 1.45b 1.68c 1.34bd 1.28d

Finishing performanceADG, lb. 3.16bc 3.44c 2.45f 2.73ef 2.36f 2.94bc 3.92d 3.46c

DMI, lb/d 25.8ab 27.1bc 25.8c 27.0d 27.3d 26.1b 28.7f 28.2e

Feed/Gain 8.40b 8.04b 11.15d 10.19cd 12.95e 9.09bc 7.43b 8.35b

DOFf 93 93 93 93 93 93 86 86Carcass data

Back fat, in .39bcd .40bd .32cd .44b .37cd .38bcd .39bd .40bd

Ribeye, sq in 13.22b 13.39b 13.07bd 13.08bd 12.46bd 13.39b 14.20c 13.74bc

Percent choice 37.5 77.3 31.3 50.0 37.5 43.8 68.8 37.5Yield grade 2.13bc 2.46cd 2.06b 2.69d 2.25bc 2.31bc 2.25bc 2.44cd

aBG=smooth brome continuous, BG-WS=smooth brome rotation with warm season, OATS=oats pasture, CS=cornstalks, DRC=dry-rolled corn and BYP=byproduct.b,c,d,e,fMeans with unlike superscripts differ (P<.05)gDays on feed.

Table 5. Economical analyses by treatment for steer in different growing-finishing combinations.

Removal: Early (12/1/96) Late (1/13/97)

BGa BG BG-WS BG-WS BG BG BG BGCS OATS CS OATS CS OATS CS CS

DRC DRC BYP BYP BYP BYP DRC BYPItem 1 2 3 4 5 6 7 8

Steer cost, $b 478.81 479.05 479.74 479.50 480.20 480.51 480.08 482.52Interestc 36.13 36.15 36.20 36.18 36.23 36.26 40.13 40.33Healthd 15.00 15.00 15.00 15.00 15.00 15.00 15.00 15.00Summer & fall costs, $

Grazinge 59.48 86.10 59.48 86.10 59.48 86.10 64.40 64.40Supplementf 10.24 10.24 10.24 16.8 16.8

Finishing costs,Yardageg 28.2 28.2 28.2 28.2 28.2 28.2 25.8 25.8Feedh 123.01 129.10 103.83 108.85 109.8 105.0 125.71 104.42

Total costs, $i 764.51jkl 789.04m 747.35j 768.91kl 753.94jk 766.10jkl 783.27lm 764.25jkl

Final weight, lbp 1173jh 1258k 1129mn 1236kl 1094m 1193jl 1255k 1203jl

Slaughter Breakeven,$/100 lba 65.71jl 62.91jk 66.45l 62.48k 69.27m 64.33jkl 62.59k 63.63jk

aBG=smooth brome continuous, BG-WS=smooth brome rotation with warm season, OATS=oats pasture, CS= cornstalks, DRC= dry-rolled corn andBYP=byproduct.bInitial weight × $83/100 lb.c9% Interest rate=Steer cost × (days owned × 9% annual interest)/365 d.dHealth costs=implants, fly tags, antibiotics, etc.eBromegrass=$.35/hd/day, warm season $.35/hd/day, oats $.69/hd/d, cornstalks $.12/hd/day.fSupplement=$.16/hd/day during fall on cornstalks.gYardage=$.30/hd/day.hFeed=Dry-rolled corn $.0489/hd/d, and all-byproduct $.0413/hd/day. Plus 9% interest for half the feed.iIncludes a 2% death loss.j,k,l,m,n,oMeans with unlike superscripts differ (P<.05).pCalculated from carcass weight ÷ .62.qCalculated with last 5 year average corn price of $2.36/bu.


of fat cover and yield grades 2.06 to2.69. These are below industry aver-ages. The cattle were finished with mini-mal time in feedlot, however, some ofthe cattle were produced with no grainfeeding.

Dry-rolled corn diets producedlower slaughter breakevens than by-product diets ($62.73/cwt vs $65.23)even though the cost of the byproductdiets was less (Table 5). This resultedfrom poorer feed efficiency from thebyproduct diets. Additional fat in thediet might have been economical,

based on the improved feed effi-ciencies in the lamb experiment.

Slaughter breakevens averaged lessfor cattle grazing oats compared to thosegrazing cornstalks ($63.24 vs $65.53/cwt) even though grazing oats was moreexpensive. The good gains on oats whichcarried through the feedlot phase in-creased carcass weights and reducedthe breakevens. Grazing warm-seasongrass during the summer reducedbreakevens, compared to grazing bro-megrass alone ($64.46 vs $65.55/cwt).Extra gain from late grazing reduced

breakevens compared to similar treat-ments removed in November ($63.11vs $67.14/cwt). Lowest breakevensincluded oats grazing in early fall orlate removal from cornstalks in Jan-uary and dry-rolled corn diets forfinishing.

1Ramiro Lucena, graduate student; TerryKlopfenstein, Professor, Animal Science, Lincoln;Mark Klemesrud and Rob Cooper, researchtechnicians.


Effect of Winter Gain on Summer Rate of Gainand Finishing Performance of Yearling Steers

Dale DownsGalen Erickson

Don AdamsTerry Klopfenstein1

Steers wintered at 1.7 lb/daymaintained approximately 80% ofthe weight advantage over steerswintered at .7 lb/day during sum-mer grazing, justifying a rate ofwinter gain greater than .7 lb/day.

Summary

The effect of winter rate of gain onsubsequent grazing and finishing per-formance was evaluated using 80 me-dium-framed steers. During the winterperiod, steers were fed to achieve gainsof approximately .7 (low gain; 40 head)or 1.7 lb/day (high gain; 40 head).Warm-season Sandhills range wasgrazed by 20 low-gain and 20 high-gain steers, while the other 40 grazedbromegrass pasture from May to Sep-tember. Both low- and high-gain cattlegrazing brome pasture gained slowerthan those grazing sandhills range.During summer grazing, low-gain cattlegained faster than high-gain cattle, butcompensated for only 19.9% (sandhills)and 18.7% (brome) of the weight defi-

cit following the low-gain winter treat-ment.

Introduction

In Nebraska, management of me-dium-framed yearling steers from wean-ing to slaughter commonly consists of awinter and summer growing period fol-lowed by a relatively short finishing.These three phases have been found tobe interactive relative to effects of pre-vious nutrition on gain and efficiency insubsequent phases. That is, cattle sub-jected to nutritional restriction normallyexhibit compensatory growth duringsubsequent periods of higher nutrientintake. Due to this response, acceler-ated rates (1.75-2.75 lbs/day) of wintergain may not translate into either heaviercattle at the end of summer grazing orfewer days in the feedlot. Consequently,harvested feeds or commercial supple-ments used to elicit higher winter gainsmay not be economical when consider-ing the entire system. The potentialexists to lower feed input costs duringthe winter and allow for compensatorygain during summer grazing. However,the optimum rate of winter gain inyearling systems remains an elusiveand important question.

In Nebraska, yearlings are commonlygrazed in the summer for 90 or more

days during the grazing season beforebeing placed in the feedlot. To avoidextra cost of ownership, if may be ben-eficial to remove cattle from grass ear-lier if gains are declining. To assistdecision making of grazing seasonlength, live weight-gain patterns of year-lings grazing various forages would bea useful tool. These growth patterns,however, may vary with previous nutri-tion and forage quality, further empha-sizing the importance of this informationto the yearling producer.

The objectives of this research wereto evaluate the effect of winter gain onboth summer rate of gain and finishingperformance and to describe summerlive weight gain patterns of grazingyearling steers.

Procedure

Eighty medium-framed, British-breed steers (497 lb) were used in a 2 x2 factorial treatment arrangement withrate of winter gain and summer grazingforage type (location) as factors. Fortysteers were assigned randomly to a lowrate and 40 to a high rate of winter gain(approximately .7 and 1.7 lb/day,respectively). Following the winterperiod, 20 from each group wereassigned to graze warm-season range in


the Nebraska Sandhills or bromegrasspasture in Eastern Nebraska.

During the 163-day winter period,steers first grazed cornstalks, followedby the feeding of bromegrass hay andcorn gluten feed to achieve desired win-ter gains. Steers were implanted withCompudose before summer grazing. OnMay 6, steers were placed on summerrange/pasture and grazed until Septem-ber 6. Steers in the Nebraska Sandhillsgrazed primarily warm-season pasturedominated by little bluestem, prairiesandreed, sand bluestem, blue gramaand switchgrass. Steers assigned to East-ern Nebraska grazed smooth brome-grass. All animals were allowed accessto a trace mineralized salt block through-out the winter and summer periods.Using ruminally fistulated steers, dietsamples were taken at both locationsthroughout the summer grazing seasonand analyzed for CP and digestibility.Initial and final weights for the winterand summer phases were determinedusing the average of weights taken ontwo consecutive days following a five-day limit feeding period.

In order to describe live weight gainpatterns during summer grazing, anautomatic scale system was used toweigh individual steers each time theywatered. If steers were weighed morethan once daily, the minimum indi-vidual weights were used to calculate adaily mean for each treatment group.

Following removal from pas-ture, steers were implanted with Revalorand finished (10 head/pen) on a dry-rolled corn and corn gluten feed baseddiet (7.5% roughage) until an estimated.5 inch fat thickness was reached. Finalweights were calculated using hot car-cass weights assuming a common dress-ing percentage (62%). Liver abscessscores and hot carcass weights weretaken at slaughter and fat thickness atthe 12th rib, quality grades and yieldgrades were recorded following a 48-hour chill.

Results

Cattle on both the high- and low-gain winter treatments grazing bromepasture gained slower (P < .05) than

Table 1. Steer performance for winter, summer and finishing periods.

Sandhills Range Bromegrass Pasture

Winter Gain

Item Low High Low High

WinterDays 163 163 163 163ADG, lb/d .70a 1.67b .68a 1.68b

Final weight, lb 611a 769b 608a 771b

SummerDays 123 123 123 123ADG, lb/d 1.92a 1.66b .73c .48d

Final weight, lb 846a 973b 697c 830a

FinishingDays 99 71 124 99ADG, lb/d 4.17a 4.57ab 4.48a 5.03b

DMI, lb/d 28.8a 31.3ab 28.6a 31.7b

Feed/gain 6.91a 6.84a 6.40b 6.31b

Final weighte, lb 1262ab 1309ab 1249a 1323b

Yield grade 2.84a 2.37b 2.80a 2.95c

Fat thickness, in .51ab .44a .48ab .53b

Percentage of choice 90 58 100 79

a,b,c,dMeans with unlike superscripts within a row differ (P < .05).eBased on hot carcass weight adjusted to a common dressing percentage (62%).

Figure 1. Summer weight gain patterns of steers grazing sandhills range.

1100

1000

900

800

700

600

Live

Wt (

lb)

5/6 5/30 6/24 7/19 8/14 9/8

Date

High winter gain

Low winter gain

those grazing sandhills range (Table 1).At both locations, steers wintered at alow rate gained faster (P < .05) thancattle on the high-winter gain treat-ment, exhibiting a degree of compensa-tory growth. The higher summer gainsallowed steers to compensate for 19.9%(sandhills) and 18.7% (brome) of theweight deficit resulting from the low-gain winter treatment.

Figure 1 shows summer live weight

gain patterns of steers grazing Sandhillsrange from the low- and high-gain win-ter treatments. Figure 2 shows weightgain patterns of steers grazing brome-grass pasture. Gains of cattle on sandhillsrange appeared to be linear or constantthroughout the grazing season. Incontrast, cattle grazing bromegrassappeared to gain rapidly from May tolate June and leveled off for the remain-der of the season. Steers on the low- and


Figure 3 shows the CP and digest-ibility changes from May to August atboth locations. Protein levels of dietscollected from bromegrass pasture im-ply crude protein did not limit cattleperformance to the extent observed.Digestibility of bromegrass decreasedfrom approximately 70% to 45% dur-ing the grazing season, while digest-ibility of sandhills range remainedrelatively constant. Digestibility val-ues of bromegrass diets reflect rapidforage growth and maturation duringthe summer and help explain the largeperformance differences between loca-tions.

During finishing, high-winter-gaincattle summered on brome exhibitedhigher (P < .05) finishing ADG andDMI than low-gain steers at either loca-tion. Low- and high-winter-gain cattlegrazing bromegrass were more effi-cient (P < .05) than steers grazingsandhills range. The greater efficiencyof cattle grazing bromegrass was due toa combination of less weight (low-gaincattle) and less condition upon enteringthe feedlot. Low-gain cattle from bothlocations were on feed for more daysthan high-gain cattle. High-gain steerssummered on sandhills range exhibitedthe lowest (P < .05) yield grade, whereashigh-gain steers grazed on bromegrasshad the highest (P < .05) yield grade.Quality grade and liver abscess scoreswere affected neither by winter treat-ment nor location.

At both locations, steers on the high-winter-gain treatment maintained ap-proximately 80% of the weightadvantage over steers on the low-gaintreatment through the summer grazingperiod. Relative to the low-gain wintertreatment, higher winter gain producedheavier steers following summer graz-ing which finished with fewer days onfeed, justifying a rate of winter gaingreater than .7 lb/day.

1Dale Downs, graduate student; GalenErickson, graduate student; Don Adams, Professor,Animal Science, West Central Research andExtension Center, North Platte; Terry Klopfenstein,Professor, Animal Science, Lincoln.

Figure 2. Summer weight gain patterns of steers grazing bromegrass pastures.

Figure 3. Crude protein and digestibility of summer diets collected from brome pasture andsandhills range.

high-gain winter treatments at eachlocation seemed to exhibit similargrowth patterns during summer grazing.The compensatory growth of the low-gain winter cattle most likely occurredgradually, making it difficult to ob-serve a difference in live weight gainpatterns between the two groups.

The pasture gains on bromegrasswere much lower than in previous years,and is an illustration of the commonlyobserved “summer slump” of cattle graz-ing cool-season pasture. Due to severalfactors, the growth pattern of brome in

1996 was not conducive to optimalcattle performance relative to previousyears. May was both unseasonably cooland wet, promoting rapid growth ofbromegrass. Because of this, foragequantity exceeded animal demand earlyin the season, allowing maturation andreduction in quality. Cattle were thenforced to graze mature bromegrass inlate June and July and considerabletrampling occurred. Trampling, in com-bination with less-than-optimal tem-perature and moisture in June and July,caused limited forage availability inAugust.

900

800

700

600

500

Live

Wt (

lb)

5/6 5/30 6/24 7/19 8/14 9/8

Date

High winter gain

Low winter gain

30

25

20

15

10

5

0

CP

(%

of D

M)

5/15 6/3 6/22 7/11 7/30 8/18

Date

80

70

60

50

40

30

20

10

0

IVD

MD

(%

of D

M)

SandhillsIVDMD

BromeIVDMD

Brome CP

Sandhills CP


Summer and Fall Forage Grazing Combinations:Five-Year Summary

lot. Beef production systems basedlargely on forages are often economicalbecause cost of gain during the grazingperiod is typically lower than that of ahigh-concentrate diet. Maximizing graz-ing gain while production costs willlower the slaughter price required tobreak-even.

In eastern Nebraska, brome is thepredominant grazing forage available.Brome, however, is a cool-season plantand both the quality and quantity ofbrome can decline during the months ofJune, July and August. Furthermore,grazing a single forage for the entiregrazing period may not allow for maxi-mum gain because of quantity and qual-ity of forage. Using alternative orcomplementary forages is one methodavailable to balance the distribution offorage growth with the nutritional needsof livestock.

Previous Nebraska Beef Cattle Re-ports have provided the results of re-search on forage combinations forsummer and fall grazing, compared withgrazing only one plant species for theentire grazing period. Although theseindividual reports are important, yearlyvariation in environmental factors mayinfluence interpretation. This article isa summary of five years of data involv-ing the influence of grazed forage com-binations on summer and fall beef cattlegains and evaluates effects of thesecombinations on economics of the en-tire growing/finishing system.

Procedure

Data collected during five years wasused to evaluate grazing alternative for-ages during the summer and fall of eachyear. In each year, British-breed calveswere purchased in the fall and alloweda 28-day receiving and acclimationperiod. Calves were assigned to a low-

input wintering period: either grazingcornstalk residue or feeding harvestedforages. All calves were fed a proteinsupplement and allowed free access toa mineral supplement during the stalkgrazing and harvested forage feedingperiods. Following the winter and springfeeding periods, calves were assignedto grazing treatments.

Summer-forage cattle continuouslyor rotationally grazed from the firstweek of May to the first week of Sep-tember while fall-forage cattle grazedfrom the first week in September tomid-November. All cattle were im-planted with Compudose before sum-mer grazing.

Following grazing, cattle were fin-ished on a high-concentrate corn-basedfinishing diet formulated (DM basis) tocontain 12% CP, .7% calcium, .35%phosphorus, .7% potassium, 25 g/tonmonensin and 10 g/ton tylosin. Initialand final weights for each stage werethe average of two weights taken onconsecutive days following a three-dayfeeding of a 50% alfalfa hay and 50%corn silage diet (DM basis). Intakesduring these periods were limited to 2%(DM) of body weight. Final weightswere estimated from hot carcass weightusing a 62 dressing percentage. Carcassmeasurements included hot carcassweight, liver abscess score, fat thick-ness, quality grade and yield grade.

Breakeven cost was used as the mea-sure of success of each system andincluded all input costs. Feedlot penwas used as the observation unit forstatistical analysis. Breakeven correla-tion coefficients (r) for amount of gainachieved during the winter/spring pe-riod, summer grazing, combined sum-mer and fall grazing and finishingperiods were determined to evaluatewhich period within each system hadthe most influence on breakeven cost.

Drew ShainTerry Klopfenstein

D. J. JordonRick Stock1

Summer and fall forages thatmaximize grazing gain in growingfinishing systems can reduceslaughter breakeven costs.

Summary

A five-year study using British-breedcrossbred cattle included slaughterbreakeven analysis and evaluatedthe effect of grazing alternative sum-mer and fall forages on beef produc-tion systems. Grazed summer and fallforage combinations included con-tinuous brome and combinations ofbrome, warm-season grasses, alfalfa,sudangrass, red clover, native Sand-hills range, turnips, rye and corn-stalks. The most consistent improve-ment in summer grazing gain andmost desirable slaughter breakevencosts were observed in cattle grazingbrome and warm-season grasses orbrome and Sandhills range. A reduc-tion in slaughter breakeven cost bygrazing fall forages was observed inyears with adequate moisture forforage growth. Forages maximizinggrazing gain most greatly reducedslaughter breakeven cost.

Introduction

Grazing summer and fall forages isan important component of extensivebeef production systems. These sys-tems include a backgrounding periodduring the winter and spring and asummer and/or fall grazing period fol-lowed by a finishing period in the feed-


Results

In this report, data were pooled fromsimilar grazing treatments wheneverpossible and analyzed across years. Asummary of data for grazing treatmentsunique to one year, however, arepresented in this report with actual datareported in previous Nebraska BeefCattle Reports.

Summer Forages

Grazing brome, then either alfalfa,sudangrass or warm-season grasses,improved summer gains compared withcattle grazing only brome (NebraskaBeef Cattle Report, MP 58. pp. 21).However, cattle grazing only bromewere more economical (lower slaugh-ter breakeven cost) than cattle grazingbrome and sudangrass. Grazing bromeand alfalfa or sudangrass increased graz-ing gain compared to grazing bromealone. However, the added cost of al-falfa or sudangrass production resultedin higher breakeven costs for these sys-tems when compared to grazing bromealone or brome and warm-seasongrasses. In our research, the cost ofproducing sudangrass and alfalfa waspriced equal to the cost of cash-rentingland for corn production plus plantingcosts. Poloxalene on alfalfa for bloatcontrol adds to the costs. Therefore, theadditional summer gain achieved bygrazing alfalfa or sudangrass did notoffset the additional cost of producingthe forage.

Reducing forage production cost byinter-seeding red clover in oats andcharging land and production costsagainst the oats provides an alternativeforage for grazing while keeping thecost of the grazed forage to a minimum.However, grazing only red clover has apotential bloat-causing risk. Providingpoloxalene to legume-grazing cattle canoffset the potential bloat problem, as-suming poloxalene consumption is con-stant.

In a subsequent year (Nebraska BeefCattle Report, MP 61. pp. 20), systemsincluding red clover grazing had themost desirable slaughter breakeven costswith grazing gains similar to other sys-tems. However, bloat problems requir-

ing removing the cattle from the redclover pastures and placing them backon brome pasture. So, although grazingred clover as an alternative forage im-proved slaughter breakeven costs, thepotential cattle loss due to bloat madethe system less desirable due to extracosts of poloxolene supplement andlabor to treat animals experiencing bloat.

If either sudangrass or alfalfa wereused in lands unsuitable for grain pro-duction, grazing costs would equal thecost of producing the forage (seed, plant-ing, labor, etc.), which would, in turn,lower the system’s slaughter breakevencost. Grazing red clover following har-vest of a grain crop appears to havepotential in improving production sys-tems. Grazing alfalfa, sudangrass or redclover monocultures in addition tobrome either proved not economical orpotential bloat problems made thesesystems less desirable.

In two successive years (NebraskaBeef Cattle Report, MP 66. pp. 48;Nebraska Beef Cattle Report, MP 67.pp. 56), native grass resources wereutilized in the Nebraska Sandhills toprovide a mix of warm-season grassesas an alternative to establishing bothcool- and warm-season grass pasturesat one location. Grazing a native rangewith a diversity of plant species allowscattle to select higher-quality forage. Inboth years, summer gains for cattlegrazing systems utilizing Sandhills

range, either alone or in combinationwith brome grazing, were greater(P<.05) compared with cattle grazingonly brome, brome and red clover orbrome and warm-season grasses (Table1). However, slaughter breakeven costsfor cattle grazing systems utilizingSandhills range, brome and red cloveror brome and warm-season grasses weresimilar. Cattle grazing continuousbrome had the least desirable (P<.05)breakeven cost (Table 1).

Inter-seeding red clover in bromepastures was one attempt at increasingforage quality and quantity during peri-ods when brome quality and quantity isdeclining. However, stands of red clo-ver inter-seeded in brome pastures werepoor in both years. Although gains werenot statistically different between cattlegrazing red clover/brome and continu-ous brome, these results indicated inter-seeding red clover in brome pasturescould potentially improve grazing gainscompared to cattle grazing only brome.

Data for similar grazing systems(continuous brome and brome/warm-season grass) were pooled and analyzedacross years. Cattle grazing brome andwarm-season grasses had greater(P<.05) daily gains during the summercompared with cattle grazing onlybrome (Table 2). During finishing, cattlein the continuous brome systemconsumed more feed (P<.05), gained


Table 1. Performance and economics for steers grazing brome, brome and warm-season grasses,brome and red clover, brome and Sandhills range or only Sandhills range - a two yearsummary.

Forage System: Summer Forages

Brome, Brome, Brome,Cont. red warm- Sandhills Sandhills

Item brome clover season range range

Weight, lbInitial 488 483 480 478 484Initial summer 629 624 618 623 625End summer 805 828 824 883 887Final 1212 1247 1231 1247 1242

Finishing performanceDMI, lb/day 29.10a 29.43a 28.10b 29.84a 29.33a

Daily gain, lb 3.95 4.09 3.98 4.17 4.03Feed/gainc 7.40 7.19 7.09 7.19 7.30

Total costs, $d 811.13 812.20 806.74 782.27 785.62Slaughter Breakeven,

$/100 lb 67.01a 65.12b 65.13b 63.67b 64.16b

a,bMeans in rows with unlike superscripts differ (P<.05).cFeed/gain analyzed as gain/feed. Feed/gain is the reciprocal of gain/feed.dIncludes trucking cost to (one way) Sandhills range increasing breakeven $.912/cwt.


Fall forage grazing gains were vari-able among years, probably due to pre-cipitation variation among years. Duringyears where lack of precipitation re-duced fall forage quality and quantity,grazing gains were low and slaughterbreakeven costs increased. Gains forcattle grazing turnips were variableamong years compared with other for-ages. Potential yearly variations inmoisture, resulting in variable foragequantity from turnips, makes the use ofturnips in fall grazing systems less reli-able. Grazing rye seeded in wheatstubble appears to have gain-improvingpotential, but the cost of herbicide toremove rye from the fields in the springmakes this system less desirable.

Quantity and quality consistency of

Table 2. Performance data pooled across fiveyears for cattle grazing continuousbrome or brome and warm-seasongrasses.

Brome,Continuous warm-

brome seasonItem Treatment: 1 2

Weight, lbInitial 453 448Initial summer 583 577End summer 771a 796b

Final 1154 1175

Daily gain, lbWinter .68 .68Summer 1.59a 1.81b

Finishing performanceDMI, lb/day 26.76a 25.76b

Daily gain, lb 3.59 3.58Feed/gainc 7.46a 7.25b

Carcass dataFat depth, in .42 .42Quality graded 18.7 18.7Yield grade 2.39 2.34

a,bMeans in rows with unlike superscripts differ (P< .05).cFeed/gain analyzed as gain/feed. Feed/gain isreciprocal of gain/feed.d20=average Choice, 19=low Choice, 18=highSelect.

Table 3. Economic data pooled across yearsfor cattle grazing continuous bromeor brome and warm-season grasses.

Brome,Continuous warm-

brome seasonItem Treatment: 1 2

Steer cost,$a 361.88 358.40Interestb 46.10 45.90Healthc 25.00 25.00

Winter costs,$Feedd 78.95 78.95Supplemente 19.42 19.42

Summer costs,$Grazingf 40.98 41.94

Finishing costs,$Yardageg 31.92 31.76Feedhi 173.63 167.08Days on feed 106.4 105.9

Total costs, $j 775.47 765.87Final wt, lbk 1154 1175Slaughter Breakeven,

$/100 lb 66.99l 64.99m

aInitial weight x $80/cwt.b9% interest rate.cHealth costs = implants, fly tags, etc.dReceiving costs at $.64/d, Stalk grazing costs at$.12/d; spring feed costs at $.40/d; receiving,winter, and spring yardage costs at $.10/d.eSupplement cost at $.12/d; 1.5 lb/d (as fed).fGrazing costs = $.35/hd/d.gYardage cost $.30/hd/d.hAverage diet cost = $.0543/d (DM) and 9% interestfor 1/2 of feed.iCalculated using 15 year average corn price =$2.41/bu.jTotal costs includes 2% death loss for each system.kCalculated from hot carcass weight adjusted for62% dressing percentage.l,mMeans in rows with unlike superscripts differ(P<.05).

similarly and had lower feed efficien-cies (P<.05) compared with cattle inthe brome, warm-season grass system.No difference in carcass measure-ments were observed between treat-ments. Cattle grazing brome and warm-season grasses had more desirableslaughter breakeven costs comparedto cattle continuously grazing brome(Table 3). Cattle from the brome andwarm-season grass system enteredthe finishing period with heavierweights and were able to maintainthis weight advantage throughoutfinishing.

Fall forages

Extending grazing past the summerhas the potential for further increases inweight gain from forage, reductions inthe amount of grain fed and time spentin the finishing phase and improve-ments in reducing overall slaughterbreakeven values. However, extendingthe grazing season also increases inter-est cost charged against the animal.Therefore, it is critical fall grazing gainsoffset the increased interest cost.

fall forage are major considerations infall grazing systems. If grazing gainsare not sustained during the fall, theincreased interest cost and lighter weightof cattle entering the finishing phasewill increase slaughter breakeven costs.The most consistently available fallforage available for grazing may becornstalks.

When cattle enter the finishing phase,following a period of forage grazing,the majority of muscle growth has al-ready occurred. However, sufficient fin-ishing time is still required for cattle todeposit intramuscular fat to improvequality grade. Reducing the amount oftime cattle spend in the finishing periodwithout reducing quality grade or fatthickness is one goal of fall grazing. Inall years, cattle grazing fall forageswere in the finishing phase 16 days lessthan cattle finished following summergrazing.

In evaluating correlation coefficientsamong years (Table 4), final finishingweight was negatively correlated(P<.01) with slaughter breakeven costin all years, indicating a greater finalweight lowers breakeven cost. Finish-ing period daily gain influenced (P<.01)slaughter breakeven cost in two yearsonly, while the amount of summer gainor total grazing gain influenced (P<.10)breakeven cost in four of five years.The influence of the amount of weightgain achieved during the fall grazingperiod reduced breakeven cost in oneyear but increased it in another.

The influence of total grazing gainwas negatively correlated (P<.03) withdays on feed in the finishing period inall years (Table 5) indicating that maxi-mizing forage gain can reduce timespent in the finishing period. The influ-ence of total grazing gain on finishingperiod daily gain, dry matter intake andfeed efficiency was variable amongyears.

In conclusion, grazing forages thatmaximized grazing gain, while cost ofgain is fixed, reduced overall breakevencost of production. The most consistentforage combinations in increasing graz-ing gain and reducing breakeven costwere combinations of brome, warm-season grasses and native range grasses.Grazing forages during the fall may


Table 5. Correlation coefficients (r) for total grazing gain affecting days on feed, daily gain, feedefficiency, and dry matter intake in the finishing period.

Year 1 Year 2 Year 3 Year 4 Year 5

Variable r P= r P= r P= r P= r P=

-------------------------------------Total grazing gain-----------------------------------

Days on feed -.97 .001 -.88 .001 -.86 .001 -.56 .026 -.93 .001

Daily gain -.86 .001 .15 .559 -.37 .199 .11 .683 -.75 .003

G/F -.87 .001 -.22 .386 -.56 .038 -.39 .140 -.79 .001

DMI .15 .575 .70 .002 .35 .220 .70 .003 .35 .158

Table 4. Correlation coefficients (r) for winter, summer, fall, total grazing and finishing gains, andfinal weight effects on slaughter breakeven cost.

Year 1 Year 2 Year 3 Year 4 Year 5

Variable r P= r P= r P= r P= r P=

Winter gain -.24 .379 -.37 .128 -.34 .236 -.09 .750 -.24 .337

Summer gain -.16 .544 -.46 .056 -.85 .001 -.74 .001 -.81 .001

Grazing gain .61 .013 -.44 .067 -.69 .007 -.39 .140 -.54 .021

Fall gain .70 .003 -.31 .215 -.47 .092 .28 .287 -.08 .757

Finishing gain -.73 .002 -.31 .210 .13 .669 -.72 .002 .23 .343

Final weight -.73 .002 -.89 .001 -.85 .001 -.78 .001 -.66 .003

potentially reduce breakeven cost com-pared with grazing only summer for-ages. However, variable moisture forfall forages results in unpredictablegrazing gains and subsequent break-even costs in fall grazing systems.

A beef production system must beable to withstand yearly environmentaldifferences, such as moisture and tem-perature which influence quality andquantity of available forage. Althoughsummer gains during this study weredifferent among years, differencesamong grazing systems should reflectthe systems ability to maximize graz-ing gain.

1Drew Shain, former technician; TerryKlopfenstein, Professor, D. J. Jordon, graduatestudent, Animal Science, Lincoln; Rick Stock,Cargill, Blair, NE.


Metabolism and Digestibility of Corn Bran andCorn Steep Liquor/Distillers Solubles

Tony ScottTerry Klopfenstein

Rick StockRob Cooper1

Corn steep liquor/distillerssolubles lowered pH while feedingcorn bran tended to increase pH.Corn steep liquor/distillers solublesfed alone changed the ruminal fer-mentation pattern of steers.

Summary

Six ruminally cannulated steers andsix intact steers were used in a 6x6Latin square design to determine theeffect of corn bran and/or corn steepliquor/distillers solubles on ruminalmetabolism and digestibility. Steers fedcorn steep liquor/distiller’s solubleshad lower average daily pH. Corn bran

helped maintain a higher average pH.Corn steep liquor/distillers solubles fedalone altered the fermentation patternof steers. There was a tendency for cornbran to reduce digestibility and forcorn steep liquor/distillers solubles toimprove digestibility.

Introduction

The corn wet milling industry con-tinues to offer Nebraska cattle feedersopportunities to include byproduct in-gredients in their finishing diets. In-cluding byproducts in cattle rationsrequires a fundamental working knowl-edge of their effect on nutrient metabo-lism and their overall effect on animalperformance. Corn bran is the fibrousfraction left after corn is wet milled.Corn steep liquor contains the solublefraction (amino acids, peptides, vita-mins, minerals, etc.) of the corn, as wellas lactate and other fermentation

endproducts. Processing plants produc-ing ethanol have distillers solubles thatalso may be added back to the cornsteep liquor. Previous research at theUniversity of Nebraska has shown asignificant interaction between cornbran and corn steep liquor/distillerssolubles for gain efficiency . This ex-periment was designed to determine theeffect of corn bran, corn steep liquor/distillers solubles and combinations ofthe two feed ingredients on metabolismand digestibility.

Procedure

Six ruminally cannulated (873 lb)and six intact (872 lb) steers were usedin a 6 x 6 Latin square design (2). Theexperimental treatment structure was a2 x 3 factorial with treatments basedupon adding corn bran (B), corn steepliquor/distillers solubles (ST) and com-


Table 2. Intake and pH data from cannulated steers.

Dieta

15B- 15B- P=bc

Item DRC 15ST 30ST 15B 15ST 30ST B STBxST

DMI, lb 18.7 20.7 17.9 20.2 20.2 21.3 .15 ns nsMax pHd 6.59 6.59 6.40 6.76 6.61 6.45 ns .06 nsAvg pHe 6.01 5.92 5.75 6.12 5.95 5.92 .14 .03 nsMin pHf 5.42 5.42 5.25 5.43 5.35 5.50 — — .06pH<5.6 x ming 26.8 28.6 138.9 26.2 48.6 5.1 — — .01

aDRC = dry-rolled corn; B = corn bran; ST = steep liquor/distillers solubles.bEquals P value for effect of corn bran, effect of steep liquor/distiller’s solubles and corn bran x steepliquor/distiller’s solubles interaction.cns = not significant (P > .20).dMax pH = maximum pH.eAvg pH = average pH.fMin pH = minimum pH.gpH<5.6 x min =pH x minutes below pH 5.6.

Table 3. Composite VFA analysis.

Dieta

15B- 15B- P=bc


Acetated 58.6 53.9 49.7 55.1 57.6 55.8 — — .09Propionatee 33.6 38.3 41.6 38.6 33.6 33.3 — — .05A:Pf 1.74 1.41 1.19 1.43 1.71 1.68 — — .09Butyrateg 2.39 2.85 2.95 1.96 3.68 4.07 .11 .01 .12Total VFA, mM 97.6 96.2 96.0 96.7 94.9 91.6 ns ns ns

aDRC = dry-rolled corn; B = corn bran; ST = steep liquor/distillers solubles.bEquals P value for effect of corn bran, effect of steep liquor/distiller’s solubles and corn bran x steepliquor/distiller’s solubles interaction.cns = not significant (P > .20).deMolar proportion.fAcetate to propionate ratio.gMolar proportion.

Table 4. Total tract digestibility.

Dieta

15B- 15B- P=bc


DMI, lb 17.3 19.4 16.1 18.1 17.9 19.0 ns ns nsDM, % 84.5 87.8 84.5 80.3 83.0 82.4 .05 ns nsCP, % 79.4 83.3 79.0 77.1 78.0 81.5 ns ns nsNDF, % 76.0 78.4 71.8 73.8 75.6 82.2 — — .05Starch, % 99.8 99.8 99.8 99.6 99.7 99.7 ns ns ns

aDRC = dry-rolled corn; B = corn bran; ST = steep liquor/distillers solubles.bEquals P value for effect of corn bran, effect of steep liquor/distiller’s solubles, corn bran x steep liquor/distiller’s solubles interaction.cns = not significant (P > .20).

binations of B and ST to a dry-rolledcorn (DRC) control diet. Treatmentswere DRC, 15%B, 15%ST, 30%ST,15%B-15%ST and 15%B-30%ST (DMbasis). Diets (Table 1) were formulatedto contain (DM basis) a minimum of13% CP, .70 % Ca, .30% P and included25 g/ton Rumensin and 10 g/ton Tylan.Steers were fed once daily and allowedad libitum access to diets. Steers wereadapted to a 92.5% concentrate diet byusing adaptation diets containing (DMbasis) 35 (9 d), 25 (9 d) and 15% (7 d)forage.

Ruminally cannulated steers wereused to continuously monitor pH andintake using the system described byCooper et al. (Nebraska Beef CattleReport, 1997 pp. 49). In addition, ru-men fluid samples were taken for VFAanalysis. Each period was 14 days: dietadaptation days 1-7, pH and intakemeasurements days 8-13, and rumenfluid sampling day 14. Samples of ru-men fluid were taken every hour for 24hours beginning at 0900 on day 14.Analyses of VFA were performed on 12and 24 hour samples and a compositesample of each of the hourly samples.

Intact steers were used to determinethe effect of B, ST or combinations of Band ST on total tract digestibility. Eachperiod lasted 14 days: diet adaptationday 1-10 and total fecal collection days11-14. Feed ingredient samples weretaken weekly and feed refusals wereweighed daily. Samples of feed refusalswere taken for days 9-12 (48 hoursbefore initiation/termination of totalfecal collection). Fecal collection bagswere weighed, sampled and cleanedtwice daily. Samples of feed ingredi-ents, feed refusals and feces were driedin a 60oC oven and composited foranalysis. Analyses included DM, CP,NDF and starch.

Results

There were no differences in DMIamong steers due to addition of B and/or ST to the DRC basal diet. Steersconsumed an average of 2.4 lb of feed ineach of 9.5 meals per day with eachmeal averaging 37.9 min. There wereno differences in the number, size orlength of meals (data not presented) due

Table 1. Diet Composition.

Dieta

Ingredient DRC 15ST 30ST 15B 15B-15ST 15B-30ST

DRC 87.5 73.5 58.5 72.5 58.5 43.5Bran 15.0 15.0 15.0Steep 15.0 30.0 15.0 30.0Alfalfa 7.5 7.5 7.5 7.5 7.5 7.5Supplementb 5.0 4.0 4.0 5.0 4.0 4.0

aDRC = dry-rolled corn; B = corn bran; ST = steep liquor/distillers solubles.bIncludes vitamins, minerals, and feed additives


to addition of B and/or ST to the diet.Laboratory analyses for CP, NDF

and starch were determined for DRC, Band ST. The CP contents were 8.2, 12.0and 26.5% for DRC, B and ST, respec-tively. Fiber (NDF) contents were 19.8,78.2 and 0.0% for DRC, B and ST,respectively. Starch contents were 80.7,23.1 and 15.0% for DRC, B and ST,respectively.

Adding ST to the diet lowered aver-age ruminal pH (Avg pH, Table 2).Corn steep liquor/distillers solubles hasan inherently low pH (4.0-4.5), as wellas an appreciable amount of lactic acidand unfermented carbohydrates. Therewas a tendency (P = .14) for B toincrease average pH. There was a B xST interaction for both minimum pHand pH<5.6 x min (Min pH and pH<5.6,Table 2). When ST was fed alone, mini-mum pH decreased and pH<5.6 x minincreased as additional ST was added.However, when B and ST were fed incombination, minimum pH decreasedat the 15% level of ST, but did notfurther decrease with additional ST.Similarly, pH<5.6 x min increased at

the 15% level of ST but did not furtherincrease at the 30% level of ST.

Analyses of VFA composite samples(Table 3) resulted in a B x ST interac-tion for molar proportion of acetate andpropionate, as well as acetate to propi-onate ratio (A:P). When ST was fedalone, acetate decreased, propionateincreased and the acetate to propionateratio decreased as level of ST increased.However, when B and ST were fed incombination, acetate, propionate andacetate to propionate ratio were similarto the DRC control, regardless of thelevel of ST in the diet. Inclusion of STin the diet increased the molar propor-tion of butyrate. Total VFA concentra-tion was not changed by feeding of Band/or ST. The fermentation patternchange that accompanied the feeding ofST alone may help to explain a previousfinding: that when ST replaced DRC inthe diet it appeared to have a higherenergy value (Nebraska Beef CattleReport, 1997 pp. 72). The high lacticacid content of ST may contribute to thechange, due to metabolism of lacticacid to propionate.

Results using intact steers showedno differences in DMI due to inclusionof B and/or ST in the diet (Table 4).Inclusion of B in the diet reduced DMdigestibility. Though highly digestible,corn bran is likely slightly less digest-ible than the DRC it replaced. Therewas a B x ST interaction for NDFdigestibility. The digestibility of CPand starch were not changed by feedingB and/or ST.

Results of this research indicate feed-ing corn steep liquor/distillers solubleslowers the average ruminal pH of steers.Feeding corn bran may help to maintaina higher average pH. The acetate topropionate ratio of steers is loweredwhen corn steep liquor/distillers solublesis fed alone. Feeding corn bran reduceddry matter digestibility.

1Tony Scott, graduate student; TerryKlopfenstein, Professor Animal Science, Lincoln;Rick Stock, Cargill Corn Milling, Blair, NE; RobCooper, research technician, Lincoln.


Effects of Feed Intake Variation on Acidosis andPerformance of Finishing Steers

Rob CooperTerry Klopfenstein

Rick StockCal ParrottDan Herold1

Intake variation of 4 lb/day didnot increase acidosis or decreaseperformance of finishing steers fedat ad libitum levels of intake. How-ever, intake variation may increaseacidosis of limit-fed steers.

Summary

Four metabolism and two finishingtrials were conducted to determine theeffects of imposed feed intake variationon acidosis and performance of finish-

ing steers. In metabolism trials, intakevariation of 3 lb DM/day increasedacidosis of limit-fed steers as measuredby ruminal pH. However, whensteers were fed at ad libitum levels ofintake, intake variation of up to 4 lbDM/day did not increase acidosis.In finishing trials, imposed intakevariation of 4 lb DM/day neitherdecreased daily gain nor feed efficiencyof steers fed at ad libitum levels ofintake.

Introduction

Feed intake variation by cattle fedhigh-concentrate diets is presumed bymost nutritionists and feedlot man-agers to either predispose or cause diges-tive disturbances such as acidosis.Despite this commonly held belief, rela-

tively few data are available to evaluateeffects of feed intake variation on aci-dosis and cattle performance. Feed in-take variation has also been describedas a sign, not necessarily a cause, ofsubacute acidosis. However, intakevariation does not always have a strongnegative correlation to cattle perfor-mance. Therefore, the cause and effectnature of intake variation and acidosisis unclear. Objectives of these trialswere to evaluate the effects of imposedfeed intake variation on acidosis andperformance of finishing steers.

Materials and Methods

Metabolism Trials.

Four metabolism trials were con-ducted to determine the effects of


imposed feed intake variation on acido-sis of finishing steers. In MetabolismTrials 1 and 2, four ruminally fistulatedsteers were used in switchback designswith three 6-day periods. Steers werepaired by previous ad libitum intakelevel and assigned an intake level, withinpair, so that the steers averaged ap-proximately 80% of ad libitum intake.In Metabolism Trial 1, treatments con-sisted of: constant amount of feed givenper day (C); and daily feed intake varia-tion of 1.5 lb/day (LV). In MetabolismTrial 2, treatments consisted of: con-stant amount of feed given per day (C),and daily feed intake variation of 3 lb/day (HV). In Metabolism Trial 3, thesame four ruminally fistulated steersfrom Trials 1 and 2 were fed at adlibitum levels and subjected to threelevels of feed intake variation: ad libi-tum intake with no imposed feed intakevariation (AL); daily feed intake varia-tion of 1.5 lb/day (LV); and daily feedintake variation of 3 lb/day (HV). Treat-ments LV and HV were based on eachsteer’s individual AL intake. TreatmentsAL, LV and HV were applied to allsteers in the 6-day periods of 1, 2 and 3,respectively. In Metabolism Trials 1, 2and 3, steers were fed a 90% concen-trate diet once daily consisting of (DMbasis) 78.5% dry-rolled corn, 10% al-falfa hay, 7.8% molasses-urea supple-ment and 3.7% dry supplement.Rumensin was included in the diets at25 g/ton.

In Metabolism Trial 4, six ruminallyfistulated steers were utilized in a split-plot, crossover design with a 2x3 facto-rial treatment structure. Treatmentsconsisted of three levels of imposedintake variation: ad libitum intake withno imposed intake variation (AL); dailyfeed intake variation of 2 lb/day (LV);and daily feed intake variation of 4 lb/day (HV). Treatments LV and HV werebased on each individual steer’s ALintake. Treatments AL, LV and HVwere applied to all steers in periods 1, 2and 3, respectively. During these peri-ods, steers were assigned randomly toone of two dietary treatments, with orwithout Rumensin at 25 g/ton. Follow-ing period 3, Rumensin treatments wereswitched, with the three steers receiv-

ing Rumensin being assigned to thecontrol diet and the three steers receiv-ing the control diet being assigned tothe Rumensin treatment. Following a15-day wash-out period, treatments AL,LV and HV were then again applied toall steers in periods 4, 5 and 6, respec-tively. Steers were fed once daily a92.5% concentrate diet consisting of(DM basis) 81.9% dry-rolled corn, 7.5%alfalfa hay, 6.4% molasses-urea supple-ment and 4.2% dry supplement.

In metabolism trials, steers were teth-ered in individual metabolism stalls.Individual feed bunks were suspendedfrom load cells and monitored continu-ously. Ruminal pH also was monitoredcontinuously with submersible pH elec-trodes suspended through the plug ofthe ruminal cannula of each steer. Eachelectrode was encased in a weightedfour-wire metal shroud to keep the elec-trode in a stationary position approxi-mately 5 inches above the ventral floorof the rumen, while allowing rumencontents to flow freely through it. Loadcells and pH electrodes were linkeddirectly to a computer, allowing dataacquisition software to record both afeed weight and ruminal pH for eachsteer every minute during the six-daycollection periods.

Finishing Trials.

Two finishing trials were conductedto evaluate the effect of imposed feedintake variation on performance of fin-ishing steers. In Finishing Trial 1, 75crossbred yearling steers (average ini-tial weight = 620 lb) were blocked byweight and assigned randomly to one oftwo treatments (4 replications per treat-ment). Treatments consisted of two lev-els of imposed feed intake variation: adlibitum with no imposed feed intakevariation (AL); or daily intake variationof 4 lb/day (HV). The finishing dietcontained (DM basis) 51.7% dry-rolledcorn, 35% high moisture corn, 5% al-falfa hay, 3.3 % corn silage and 5% drysupplement. Rumensin was included inthe diet at 25 g/ton and Tylan at 10 g/ton. Steers were implanted with Revalor-S and fed for 140 days.

In Finishing Trial 2, 94 crossbred

yearling steers (average initial weight =656 lb) were assigned randomly to oneof 12 pens. Pens were allotted randomlyto one of two dietary treatments and toone of two levels of intake variation.Dietary treatments consisted of eithercontrol diet balanced for typical com-mercial feedlot CP and P levels or a dietbalanced to match MP and P require-ments using the NRC model (1996).The control diet contained (DM basis)81.3% dry-rolled corn, 7.5% alfalfa hay,6.7% molasses-urea supplement and 5%dry supplement. The balanced diet con-tained (DM basis) 64.5% high moisturecorn, 20.1% corn bran, 7.5% alfalfahay, 5% dry supplement and 2.9% tal-low. In both diets, Rumensin was in-cluded at 25 g/ton and Tylan at 10 g/ton.Steers were fed for 147 days and wereimplanted with Revalor-S at the begin-ning, and again after 80 days on feed.Levels of intake variation consisted ofad libitum intake with no imposed feedintake variation (AL) or daily feed in-take variation of 4 lb/day (HV). Dietarytreatments were part of a separate trialwith different objectives. Therefore, theonly level of intake variation meanspresented are those which did not havea significant interaction (P > .10).

In both finishing trials, steers on theHV treatment were fed ad libitum fromday 1 through day 34. Then, based oneach pen’s average DMI from day 28through day 34, each pen was subjectedto imposed feed intake variation of 4 lb/day from day 35 through slaughter (140and 147 days on feed for FinishingTrials 1 and 2, respectively). This wasaccomplished by first decreasing thefeed offered by 2 lb from each pen’saverage DMI on day 36. Feed offeredwas increased by 4 lb on day 37, de-creased by 4 lb on day 38, increased by4 lb on day 39 and so on. In order tomaintain the average amount of feedoffered at ad libitum levels, a 1 lb/dayadjustment factor was used. For ex-ample, if feed remained in the bunk onthe morning following a low-level of-fering day (-4 lb), only 3 lbs was of-fered, decreasing the average feedoffered to the steers by 1 lb. On the otherhand, if a bunk was slick on the morningfollowing a high-level offering day,


(+4 lb), the amount offered only de-creased by 3 lb, increasing the averagefeed offered to the steers by 1 lb. Byusing this system, feed intake variationcould be imposed on individual pensbased on individual ad libitum intakes.

Results

Metabolism Trials.

In Metabolism Trial 1, no signifi-cant differences in DMI, rate of intake,

average ruminal pH or area of ruminalpH below 5.6 (P>.10) were noted be-tween treatments of C or LV of 1.5 lb/day (Table 1). In Metabolism Trial 2,no significant differences in DMI, rateof intake and average ruminal pH(P>.10) were noted between treatmentsof C and HV of 3 lb/day (Table 2).However, area of ruminal pH below 5.6was increased (P<.05) by 75 units (mag-nitude of pH below 5.6 by min) in theHV treatment compared with C.

Results of Metabolism Trial 1 indi-cate daily intake variation of 1.5 lb/daydoes not significantly alter measures ofintake or acidosis within a limit-feed-ing system. However, there were nu-merical trends for increased rate ofintake and area of ruminal pH below 5.6and decreased average ruminal pH withthe LV treatment compared with C.Results of Metabolism Trial 2 indicateintake variation of 3 lb/day increasedacidosis in steers as measured by thearea of ruminal pH below 5.6, within alimit-feeding system. In addition, rateof intake numerically increased withthe HV treatment, although not signifi-cantly. Although Metabolism Trials 1and 2 were separate, they were con-secutive and utilized the same steers.Therefore, these two trials indicate thatthere may be a linear response of in-creased acidosis with increasing levelsof imposed feed intake variation withina limit-feeding system. Note, though,that average ruminal pH would not haveprovided the same conclusions as it wasnot significantly affected in either trial.Because area of ruminal pH below 5.6should provide a more accurate mea-sure of acidosis, conclusions were basedon this parameter.

In Metabolism Trial 3, with thetreatments of AL, LV of 1.5 lb/dayand HV of 3 lb/day, no differences inDMI, rate of intake, average ruminalpH or area of ruminal pH below 5.6(P>.10) were noted (Table 3). How-ever, although not significant (P=.28,AL versus HV), area of ruminal pHbelow 5.6 numerically decreased aslevel of intake variation increased.The same steers, fed under the samegeneral conditions, responded differ-ently to imposed intake variation


Table 1. Effects of imposed low intake variation on limit-fed steers in Metabolism Trial 1.

Treatment

Item Constanta Low intake variationb SEM

Daily DMI, lb 17.9 17.4 2.2Rate of intake, %/h 53.4 67.0 31.2Average ruminal pH 5.95 5.85 .26Area of ruminal pH below 5.6c 97.7 151.7 63.7

aConstant amount of feed offered per day at approximately 80% of ad libitum intake.bDaily intake variation of 1.5 lb/day based on the level of feed offered in the Constant treatment.cArea = magnitude of ruminal pH below 5.6 by min.

Table 2. Effects of imposed high intake variation on limit-fed steers in Metabolism Trial 2.

Treatment

Item Constanta High intake variationb SEM

Daily DMI, lb 18.1 18.1 2.0Rate of intake, %/h 46.0 70.7 22.6Average ruminal pH 5.84 5.82 .23Area of ruminal pH below 5.6cd 106.2 180.9 83.7

aConstant amount of feed offered per day at approximately 80% of ad libitum intake.bDaily intake variation of 3 lb/day based on the level of feed offered in the Constant treatment.cArea = magnitude of ruminal pH below 5.6 by min.dMeans differ (P<.05).

Table 3. Effects of imposed intake variation on steers fed at ad libitum levels in MetabolismTrial 3.

Treatment

Item Ad libituma Low variationb High variationc SEM

Daily DMI, lb 21.8 21.6 21.9 4.2Rate of intake, %/h 22.2 25.6 24.5 4.1Average ruminal pH 5.63 5.63 5.67 .17Area of ruminal pH below 5.6d 227.4 187.0 180.0 87.0

aAd libitum intake with no imposed intake variation.bDaily intake variation of 1.5 lb/day based on the level of feed offered in the Ad libitum treatment.cDaily intake variation of 3 lb/day based on the level of feed offered in the Ad libitum treatment.dArea = magnitude of ruminal pH below 5.6 by min.

Table 4. Effects of imposed intake variation on steers fed at ad libitum levels in MetabolismTrial 4.

Treatment

Item Ad libituma Low variationb High variationc SEM

Daily DMI, lb 28.8 27.9 27.9 2.2Rate of intake, %/h 31.4 37.9 35.9 6.3Average ruminal pHd 5.55 5.68 5.76 .07Area of ruminal pH below 5.6de 215.8 154.1 94.7 52.6

aAd libitum intake with no imposed intake variation.bDaily intake variation of 2 lb/day based on the level of feed offered in the Ad libitum treatment.cDaily intake variation of 4 lb/day based on the level of feed offered in the Ad libitum treatment.dLinear (P<.05).eArea = magnitude of ruminal pH below 5.6 by min.


when fed at ad libitum levels of intakecompared with being limit-fed.

In Metabolism Trial 4, with the treat-ments of AL, LV of 2 lb/day and HV of4 lb/day, DMI was not affected by levelof intake variation and averaged 28.2lb/day (Table 4). Rate of intake tended(P=.13) to increase for both LV and HVcompared with AL; but the LV and HVtreatments did not differ. Average ru-minal pH increased linearly (P<.01)across the treatments of AL (0), 2 and 4lb/day of imposed intake variation, andarea of ruminal pH below 5.6 decreasedlinearly (P<.05) as level of intake varia-tion increased. Both measurements in-dicate a reduction in acidosis as thelevel of intake variation was increased.

The results of Metabolism Trials 3and 4 suggest steers fed at ad libitumlevels of intake do not experience in-creased acidosis with imposed intakevariation of up to 4 lb/day. In fact, theresults support a reduced incidence ofacidosis with increased level of intakevariation. This, however, is difficult toexplain. One explanation might be thatwhen the steers were subjected to in-take variation, days of reduced feedallowed the steers to build buffer capac-ity or base-excess, so acidosis was notinduced even with over-consumptionthe following day. However, this isspeculation. Further work with rumenand blood metabolites is needed in thisarea. One thing is clear: steers fed at adlibitum levels under these trial condi-tions did not experience more acidosiswith increased intake variation.

Finishing Trials.

Dry matter offered to pens of cattlein Finishing Trials 1 and 2 are shown inFigures 1 and 2, respectively. In thesefigures, DM offered is averaged bylevel of intake variation for day 35through slaughter. Although these fig-ures depict feed offered, actual DMIshould be similar as the daily amountoffered was adjusted so feed would notaccumulate in the bunk. The overallpattern of DMI was very similar be-tween levels of intake variation for bothtrials. However, there was a much higherdegree of day-to-day intake variation in

the pens on the HV treatments, predict-able due to the imposed intake variationof 4 lb/day. In both finishing trials, theaverage absolute daily change in amountof DM offered was 1 lb/day for AL and3 lb/day for HV. It is important to noteDMI was not constant for pens on theAL treatment, where the daily amountof feed offered was adjusted in order toavoid both feed accumulation and anempty bunk.

In Finishing Trial 1, overall DMIwas higher (P<.05) in the HV treatmentcompared with the AL treatment (Table5). However, due to intake variation, nodifferences in daily gain or feed effi-ciency (P>.10) were noted.

In Finishing Trial 2, there were nointeractions (P>.10) between dietary

treatment and imposed intake varia-tion. Therefore, only the overall meansfor intake variation are presented (Table6). No differences in DMI, daily gain orfeed efficiency were noted due to intakevariation.

The results of Metabolism Trials 3and 4 and Finishing Trials 1 and 2indicate imposed intake variation of upto 4 lb/day neither increased acidosisnor decreased performance of finishingsteers fed at ad libitum levels of intake.However, results of Metabolism Trials1 and 2 indicate intake variation in alimit-feeding system may increase theincidence of subacute acidosis.

It is important to note the intakevariation in these trials was imposedand “consistent”. Steers may have

Figure 1. Dry matter offered during Feedlot Trial 1.

32

30

28

26

24

22

20

18

DM

Offe

red,

lb

35 45 55 65 75 85 95 105 115 125 135

Days on FeedAL

HV

Figure 2. Dry matter offered during Feedlot Trial 2.

32

30

28

26

24

22

20

18

DM

Offe

red,

lb

35 45 55 65 75 85 95 105 115 125 135 145

Days on FeedAL

HV


Table 5. Effects of imposed intake variation on performance of steers fed at ad libitum levels inFinishing Trial 1

Treatment

Item Ad libituma Intake variationb SEM

Daily DMI, lbc 23.7 24.1 .1Daily gain, lb 3.75 3.84 .06Gain/DMI .159 .159 .003

aAd libitum feed offered with no imposed intake variation.bDaily intake variation of 4 lb/day from days 35 through slaughter.cMeans differ (P<.05).

Table 6. Effects of imposed intake variation on performance of steers fed at ad libitum levels inFinishing Trial 2

Treatment

Item Ad libituma Intake variationb SEM

Daily DMI, lb 24.5 24.3 .2Daily gain, lb 4.06 3.96 .05Gain/DMI .165 .163 .003

aAd libitum feed offered with no imposed intake variation.bDaily intake variation of 4 lb/day from days 35 through slaughter.

adapted to the routine of imposedchanges and therefore were lessaffected. On the other hand, randomoccurrences of intake variation, suchas a weather change or mill break-down, may increase the incidence ofacidosis. These data suggest that fin-ishing cattle can naturally vary theirintake (up to 4 lb/day and maybemore) without creating acidosis orreduced performance.

1Rob Cooper, research technician, AnimalScience, Lincoln; Terry Klopfenstein, Professor,Animal Science, Lincoln; Rick Stock, FormerProfessor, Animal Science, Lincoln; Cal Parrott,Elanco Animal Health, Greenfield, IN.; Dan Herold,research technician, Animal Science, Lincoln.

Observations on Acidosis Through Continual FeedIntake and Ruminal pH Monitoring

Rob CooperTerry Klopfenstein

Rick StockCal Parrott 1

A system of continually moni-toring feed intake and ruminal pHof finishing steers has providedmany opportunities for makinganecdotal observations of subacuteacidosis during the finishing period.

Summary

A system of continual data acquisi-tion of feed intake and ruminal pH hasbeen developed for studying subacuteacidosis in finishing steers. Feed in-take is monitored with feedbunks whichare suspended from weigh cells. Rumi-nal pH is monitored with submersiblepH electrodes suspended in the rumen.Numerous anecdotal observations ofsubacute acidosis have been madethroughout the feeding periods of sev-eral steers, providing information

unlikely to be recognized during aplanned trial. Therefore, this model forstudying subacute acidosis offers manyunique opportunities for enhancing ourunderstanding of the interactionsbetween feed intake and acidosis.

Introduction

The cattle feeding business in theUnited States has evolved into an inten-sively managed, production-orientedindustry. Due to costs associated withinterest on cattle, yardage in the feedlotand the price and inconvenience ofroughages, economics usually favorrapidly increasing the grain portion ofthe diet to put the cattle on a highconcentrate diet as soon as possible.However, both the rapid increase inconcentrate and low roughage levels inthe finishing diet increase the potentialfor subacute acidosis.

Subacute acidosis is generally char-acterized as ruminal pH between 5.6and 5.2. Ruminal pH below 5.2 is in-dicative of acute acidosis. The majorresponse seen with subacute acidosis is

reduced intake; therefore subacute aci-dosis is more subtle and more difficultto access than acute acidosis. Even inmetabolism studies it is difficult tomeasure all the effects of subacute aci-dosis, because as ruminal pH declinescattle adjust by decreasing feed intakeand alter their eating patterns. How-ever, subacute acidosis continues to bea major factor limiting feedlot cattleperformance. Several models have beenused to study subacute acidosis. Onemodel, the evaluation of intake varia-tion of individually fed cattle (1991Nebraska Beef Report, pp. 55), isbased on the premise that intake varia-tion is caused by subacute acidosis.Therefore, subacute acidosis can beevaluated by monitoring the magnitudeof feed intake variation. The secondmodel is a steer metabolism model(1993 Nebraska Beef Report, pp. 60).Fistulated cattle are challenged withsufficient grain to create subacute aci-dosis. The challenge, usually half-cornand half-wheat, is placed directly in therumen, and the ruminal pH determined



at 3-hour intervals over a 24-hourperiod. These two models have beenvery useful in the study of acidosis;however, each has limitations. Thechallenge used in the steer metabolismmodel may not be appropriate for thestudy of subacute acidosis as it mayoverwhelm the system. While erraticday-to-day intake variation is indica-tive of subacute acidosis, within-dayintake patterns have not been evaluateddirectly in the intake variance model.Therefore, it was desirable to develop amore complete subacute acidosis model.A system of continual acquisition offeed intake and ruminal pH was devel-oped so a more complete under-standing of the interactions betweenruminal pH and feed intake would bepossible.

Procedure

Continuous data acquisition of feedintake and ruminal pH has been col-lected on many steers throughout sev-eral different trials. In some of thesetrials, subacute acidosis has been mon-itored during the grain adaptationperiod. Feed intake and ruminal pHdata also have been gathered on num-erous steers during periods of subacuteacidosis induced by varying dry matterintake of steers fed a high concentratediet, directly placing grain in the rumenand late feeding. The results from thesetrials have been previously reported.However, in this report, observationsand comments will be made concerninginteresting situations and anecdotalevents which have occurred throughoutthe large amount of data collected.

During all trials in which these datawere collected, steers were tethered inindividual metabolism stalls. Feed in-takes were monitored with individualfeedbunks suspended from weigh cells.Ruminal pH was monitored with sub-mersible pH electrodes suspendedthrough the plug of the rumen cannulaof each steer. Each pH electrode wasencased in a weighted, four wire metalshroud to keep the electrode in a sta-tionary position 5 inches above the ven-tral floor of the rumen while allowingrumen contents to flow freely throughit. Weigh cells and pH electrodes were

linked directly to a computer allowingdata acquisition software to record botha feed weight and a ruminal pH everyminute for each steer during collectionperiods.

Although steers were tethered inmetabolism stalls, both intake and ani-mal performance have been favorablein all trials. It was not uncommon forthe yearling steers used in these trials toconsume over 25 lb of dry matter and togain approximately 4 lb per day.

Results

Examples of feed weight and rumi-nal pH data collected are shown inFigure 1, which depicts the two-dayintake and ruminal pH of a steer in themiddle of the finishing period. Thissteer was fed a 92.5% concentrate, dry-

rolled corn-based diet once daily at0800. Figure 1 also shows the typicalcyclic pattern of ruminal pH, which isusually highest at feeding and declinesto its lowest point 5-10 hours later. Thegraph for feed weight in Figure 1 actu-ally shows feed disappearance from thebunk. Therefore a meal is depicted whenthe feed weight line declines. As Figure1 shows, this steer ate at a more rapidrate and consumed larger meals on day1 than on day 2. The effects of theseintake patterns are reflected in theruminal pH, which dropped lower andstayed lower longer during the first daythan compared to the second. This fig-ure shows the truly cyclic nature ofruminal pH and its relationship to feedintake. Ruminal pH was relatively highat the beginning of the first day whichprobably promoted (or at least did not

Figure 1. Feed intake and ruminal pH of a steer over a two-day period on a finishing diet (92.5%concentrate).

Figure 2. Feed intake and ruminal pH of a steer during the first and second day on feed (55%concentrate).

353025

20

15

10

5

0

Fee

d W

eigh

t, lb

7.0

6.5

6.0

5.5

5.0

4.5

Rum

inal pH

Ruminal pH

Feed Weight

9:0

0

13

:00

17

:00

21

:00

1:0

0

5:0

0

9:0

0

13

:00

17

:00

21

:00

1:0

0

5:0

0

9:0

0

Time of Day

35

30

25

20

15

10

5

0

Fee

d W

eigh

t, lb

6.5

6.0

5.5

5.0

Rum

inal pH

Ruminal pH

Feed weight

8:0

0

12

:00

16

:00

20

:00

0:0

0

4:0

0

8:0

0

12

:00

16

:00

20

:00

0:0

0

4:0

0

8:0

0

Time of Day


hinder) the rapid rate of intake. As aresult of the rapid intake during dayone, ruminal pH dropped to a levelindicative of subacute acidosis. Rate ofintake was not as rapid during the sec-ond day. This is likely due to both thelow ruminal pH experienced during day1 and to a lower initial ruminal pH atfeeding time during day 2. During day2, it appears the steer consumed feed ata rate which prevented ruminal pH fromdropping to the first day’s level. It isimportant to note the steer consumedapproximately the same amount of feedon both days. However, the intake pat-terns had significant effects on ruminalpH and acidosis.

Figure 2 shows the feed intake andruminal pH of a steer which experi-enced acidosis during the first day ofstep 1 of the grain adaptation period.

Previously, this steer had been offeredalfalfa hay ad libitum. Figure 2 showsthe first and second day of step 1, a 55%concentrate dry-rolled corn-based diet.This steer consumed the diet very rap-idly on day 1, eating approximately 30lb (as-fed) in only two meals. Conse-quently, ruminal pH dropped to ap-proximately 5.0 and did not increaseuntil the next morning. The followingday, the steer was offered the sameamount of feed but did not consume ameal until about midnight and thenonly ate approximately 7 lb (as-fed) inseveral small meals. Even on only a55% concentrate diet, a steer can be-come acidotic if the diet is consumedtoo rapidly. This figure clearly showsthe relationship between feed intakeand ruminal pH and how an acidoticsteer will adjust intake to return rumi-

nal pH to a normal level. It is likely thissteer learned from this experience andwas consequently less aggressive at thefeedbunk later in the feeding period toavoid acidosis. Figure 3 shows the feedintake and ruminal pH of the same steeron day 1 and day 2 of step 2, a 65%concentrate diet (days 5 and 6 on feed).During these days, the steer ate at aslower rate, consuming small mealsthroughout the day. As a result, ruminalpH stayed relatively high and constantcompared to the two days in Figure 2.Both figures show how a steer learns toadjust intake pattern during grain adap-tation in order to avoid acidosis.

Figure 4 shows the dry matter intakeof three steers during the grain adapta-tion period. Steers were fed a dry-rolled,corn-based diet once daily at ad libitumlevels. Step-up diets consisted of 45%(d 1-5), 35% (d 6-10), 25% (d 11-15),15% (d 26-20) and 7.5% alfalfa hay(day 21-30) in place of dry-rolled corn.Figure 5 shows the average daily rumi-nal pH (average of 1,440 observationsper steer per day) of the same threesteers during the grain adaptation pe-riod. In Figure 4, notice the steer repre-sented by triangles steadily climbed inintake during step 1, but dramaticallydropped in intake the first and seconddays of step 2. Figure 5 shows that as thesteer was building intake during step 1,its average ruminal pH was steadilydecreasing, reaching approximately 5.3on the last day of step 1. Even if thissteer had not been moved to the nextstep-up diet the next day, he likelywould have decreased intake. To com-pound the steer’s existing acidosis prob-lem, step 2 (65% concentrate) wasoffered on day 6, further reducing aver-age ruminal pH and causing the steer todramatically reduce intake for severaldays. In retrospect, there may be twodifferent ways to conduct the feedcalling for this steer: 1) either offerenough feed during step 1, or extendstep 1, until this steer was “caught”(leaving feed in the bunk) reducing itsaggression during step 2; or 2) prohibitthis steer from building so high an in-take on step 1, so that the increase inconcentrate would not so drasticallyimpact ruminal pH. The latter method,


Figure 3. Feed intake and ruminal pH of same steer as in Figure 2, first and second day of step 2(65% concentrate).

9:0

0

13

:00

17

:00

21

:00

1:0

0

5:0

0

9:0

0

13

:00

17

:00

21

:00

1:0

0

5:0

0

9:0

0

35302520151050

Fee

d W

eigh

t, lb

7.0

6.5

6.0

5.5

5.0

4.5

Ruminal pH

Feed Weight

Rum

inal pH

Time of Day

Figure 4. Dry matter intake of three steers during grain adaptation.

30

25

20

15

10

Dry

mat

ter

inta

ke, l

b

0 5 10 15 20 25 30

Days on Feed

Days % Concentrate1-5 556-10 6511-15 7516-20 8521-30 92.5


however would encourage more rapidrates of intake, which can create acido-sis even with diets relatively high inroughage, as shown in Figure 2.

Figure 5 shows another interestinganecdotal event which occurred duringthese steers’ grain adaptation period.The figure shows that on day 24, aver-age ruminal pH consistently increasedfor all three steers. On this day, a feed-ing mistake occurred and the steers,which were usually fed at 0800 eachday were not fed until 1200. When thesteers were fed, they were only given 5-10 lb at a time about every two hours tohelp keep them on feed. Day 24 is thefourth day on the finishing diet (92.5%concentrate), probably one of the mostcritical days during the grain adaptationperiod. It is important to note thesesteers were at ad libitum levels of intakeand that all had some feed left in thebunk on the morning of day 24. How-ever, by 1200 all of the bunks were slickand the steers were somewhat aggres-sive. Average ruminal pH likely in-creased on this day because the steerswere out of feed for about four hours,after which they were offered feedspread out over an extended period oftime. On day 25, steers were given theirfeed as normal. Figure 5 shows thedramatic decrease in average ruminalpH on day 25 and thereafter. As indi-cated by both the very low ruminal pHand slightly reduced intakes, the steerrepresented by circles in Figure 5 suf-fered subacute acidosis for several daysfollowing the feeding mistake. It isimportant to note these values are aver-age daily ruminal pH; minimum daily

ruminal pH reached below 5.0 for allthree steers during this period. It isinteresting to note that later in this trialperiod there were unsuccessful attemptsto induce subacute acidosis by fluctuat-ing dry matter intake by 4 lb per day.Feeding four hours late had a muchmore substantial effect on acidosis thanintake variation of 4 lb per day. Thissuggests consistency and timing offeeding are critical management com-ponents in order to avoid acidosis.

These are just a few examples ofanecdotal events and observations madewith this system of continual feed intakeand ruminal pH monitoring. Often theseobservations are as interesting andinformational as the results collectedfrom the respective trial. One importantpoint needs to be emphasized. Acidosisaffects individual cattle. Through con-tinual monitoring of feed intake andruminal pH of individual steers, it isevident that virtually all steers experi-ence varying degrees of subacute aci-dosis sometime during feeding. It isunlikely, however, that these boutswould ever be noticed in a feedlot pen.Although a complete pen of cattle maynot be “off feed”, individual cattle arelikely experiencing bouts of subacuteacidosis. Many times, this acidosis goesunnoticed because individuals with re-duced intake are “averaged out” by theother cattle in the pen not experiencingacidosis.

1Rob Cooper, research technician, AnimalScience, Lincoln; Terry Klopfenstein, Professor,Animal Science, Lincoln; Rick Stock, FormerProfessor, Animal Science, Lincoln; Cal Parrott,Elanco Animal Health, Greenfield, IN.

Figure 5. Average daily ruminal pH of three steers during grain adaptation.

PhosphorusRequirement of

FinishingYearlings

Galen EricksonMark Klemesrud

Todd MiltonTerry Klopfenstein1

The phosphorus requirement forfinishing yearlings is 0.14 % ofdietary DM or less, suggesting phos-phorus supplementation in corn-based diets fed to yearlings isunnecessary.

Summary

Sixty yearling crossbred steers (849lb) were fed individually either 0.35 or0.70 % of DM as Ca and 0.14, 0.19,0.24, 0.29 or 0.34 % P. Ash content wasdetermined on bones from the lowerfront legs and one rib from each car-cass was used to determine breakingstrength. Performance and bone char-acteristics were not affected by dietaryP concentration or P intake. Steers fedthe 0.70 % Ca diets had lower gainsand poorer efficiencies when comparedto those fed 0.35 % Ca. These resultsindicate the requirement for finishingyearlings is 0.14 % P or less and it isnot necessary to supplement P in typi-cal finishing diets fed to yearling steers,as corn is usually greater than 0.25 %P.

Introduction

Manure management is a criticalissue. Phosphorus can limit the amountof manure applicable to cropland as Pdoesn’t volatilize, while 50 % or moreof the N is lost as ammonia. Given Pisn’t volatile and doesn’t leach as N,surface excesses of P can be an impor-

7.0

6.5

6.0

5.5

5.0

Rum

inal

pH

0 5 10 15 20 25 30

Days on Feed

Days % Concentrate1-5 556-10 6511-15 7516-20 8521-30 92.5


Diets (Table 1) contained 34.5 %dry-rolled corn (DRC), 22.5% brewersgrits, 22.5 % corn bran, 7.5 % groundcorncobs, 5.0 % molasses, 3.0 % fat and5.0 % supplement on a DM basis. SinceDRC contains 0.25 to 0.30 % P, brewersgrits and corn bran were fed to decreasethe dietary P level to 0.14 %. Bothfeedstuffs are high in energy and cornproducts, with grits being primarily cornstarch and bran consisting of the digest-ible corn fiber. Diets were formulatedfor 12.0 % protein and contained 25g/ton Rumensin and 10 g/ton Tylan.Steers were adapted to finisher rationsby limiting intake and gradually in-creasing DM offered until ad libitumintakes were attained. Steers were im-planted on day 1 with Revalor-S. Steerswere housed in covered pens with 30hd/pen. Initial weights were the aver-age of weights taken before feeding onthree consecutive days. Final weightswere calculated from hot carcass weightdivided by a common dressing percent-age (62). Liver abscess scores and hotcarcass weights were recorded at slaugh-ter. Quality grade, yield grade and fatthickness at the 12th rib were recordedafter a 36 hour chill.

Status of P in bone is a good indica-tor of whether the P requirement hasbeen met. The animal can not distin-guish P and only resorb that mineralfrom bone. Instead, the animal mustbreakdown the entire complex to mobi-lize P. At slaughter, two bones (firstphalanx) were collected from each frontleg to determine total mineral content.One rib was also collected from eachcarcass to determine breaking strength.After collection, each bone was trimmedof soft tissue and frozen until analysis.Phalanx bones were ashed for 24 hr at600oC to determine total mineral. Theribs were thawed and broken on anInstron Universal Testing Machine foran objective measure of bone strength.

Results

Because there were no interactionsbetween Ca and P levels, only maineffects for P (n=12) and Ca (n=30) arepresented (Table 2). Dry matter intake(DMI), ADG and feed efficiency were


Table 1. Diet composition (% of diet DM).

ITEM a Low P, Low Ca High P, Low Ca Low P, High Ca High P, High Ca

DRC 34.5 34.5 34.5 34.5BRAN 22.5 22.5 22.5 22.5GRITS 22.5 22.5 22.5 22.5COBS 7.5 7.5 7.5 7.5Molasses 5.0 5.0 5.0 5.0Fat 3.0 3.0 3.0 3.0Suppl.b 5.0 5.0 5.0 5.0

limestone 0.75 0.75 1.67 1.67salt 0.30 0.0 0.30 0.0sodium phosphate 0.0 0.72 0.0 0.73

CP 12.0 12.0 12.0 12.0Ca 0.35 0.35 0.70 0.70P 0.14 0.34 0.14 0.34

aDry-rolled corn, corn bran, brewers grits and ground corncobsbSupplement contained tr.min., vit., rumensin/tylan, KCl, urea and carrier

Table 2. Animal performance as influenced by P and Ca.

P intake ADG DMI Feed/ HCW d Fat e QG f

% P g/d lb/d lb/d gain c lb inches

0.14 15.9 3.87 25.0 6.49 776 0.41 17.90.19 19.7 3.57 22.8 6.37 755 0.40 18.70.24 27.6 3.77 25.2 6.71 776 0.42 18.50.29 32.1 3.85 24.4 6.33 774 0.43 17.90.34 36.4 3.38 23.6 7.04 745 0.43 18.9SE .74 .20 .73 21 .03 .34

% Ca0.35 3.88 a 24.4 6.29 a 776 0.41 18.20.70 3.50 b 24.0 6.90 b 755 0.43 18.5SE .13 .47 14 .02 .21

a,bMeans within a column with unlike superscripts are different (P<.05)cAnalyzed as gain to feed, the reciprocal of feed to gain.dHot carcass weighteFat depth at 12th ribfQuality grade where 18 = Select+, 19 = Choice-

tant concern if surface runoff is notcompletely controlled. Dietary manipu-lations decreasing P in the manure canalleviate some of these concerns.

Since ruminants can utilize organic(phytate) P, supplementation may notbe as critical as previously thought. Inaddition, previous research was con-ducted with younger calves which werenot fed high-energy rations and gainedless than 1 to 1.5 lbs/d. Our objectivewith this study was to determine the Prequirement of yearling cattle fed ahigh-energy diet.

Procedure

From September 4 to December 18,1996 (105 d), 60 yearling crossbred

steers (BW = 849 lb) were individuallyfed once daily using Calan gates. Steerswere randomly assigned using a 2 X 5factorial design to one of 10 treatments(6 hd/trt). Treatments consisted of twolevels of Ca, either 0.35 or 0.70 % ofdietary DM, with limestone as the sourceof supplemental Ca. Within each Calevel were five levels of P, either 0.14which contained no supplemental P,0.19, 0.24, 0.29 or 0.34 % of dietaryDM. Supplemental P was provided bymono-sodium phosphate (NaP) insteadof dicalcium phosphate to allow the Calevels to remain constant at all P levels.Two supplements (no P and high P) foreach Ca level were blended at time offeeding to achieve appropriate levels ofsupplemental P.


Table 3. Bone characteristics with main effects of P and Ca.

Phalanx Ribstotal ash % ash bone area AUCc peakd timee

% P (grams) (g/100 kg HCW) (mm2) (mm2) (lbs) (mm)

0.14 28.29 8.01 275 505 784 19.90.19 27.51 8.02 262 516 741 20.80.24 28.86 8.20 267 504 770 20.10.29 27.50 7.83 269 502 759 21.30.34 28.52 8.46 283 477 796 18.3SE .98 .20 10 30 44 1.2

% Ca0.35 28.01 7.96 269 502 735a 21.0a

0.70 28.26 8.25 273 500 805b 19.2b

SE .62 .13 6.5 19 26 .8

a,bMeans within a column with unlike superscripts are different (P<.10).cArea under curve, measure of peak force and time for breaking strength.dPeak force required to break rib.eTime required to break rib.

similar across P levels. Although in-takes were variable due to individualfeeding, no consistent trends (linear,quadratic, or cubic) were evident due toP intake. Steers fed 0.70% Ca had nu-merically lower DMI and gained slower(P<.05) than steers fed 0.35% Ca. Feedefficiency was also improved (P<.05)when steers were fed the lower level ofCa.

Bone density of the first phalanxbones, whether expressed as total gramsof mineral or as % of carcass weight,was unaffected by P level (Table 3). Ribbone area and breaking strength, whenexpressed as area under curve, peakforce in lbs or time before breaking,also were unaffected by P intake.Steers fed the higher percent Ca didnot have greater phalanx bone densityor rib bone area. Ribs from steers fed0.70% Ca required greater (P<.10)peak force but less time to break thansteers fed 0.35% Ca.

In previous studies, levels of Ca inexcess of requirement have resulted inlower intakes due to limestone’s palat-ability problems. While intakes weredepressed with the higher level of Ca,gains were similar, resulting in im-proved efficiency. The efficiency im-provement has been attributed to abuffering effect, causing less acidosis-related problems with elevated levelsof Ca. In this study, the higher Cadecreased both gains and efficiency.

Since the finisher contained 22.5% cornbran, the diet contained less starch thana typical 85 % corn diet. With lessstarch fed, acidosis problems may bereduced and any benefits from Ca buff-ering would not be evident as the resultssuggest. Decreased gains at the highlevel of Ca may be attributable to lessenergy being used for gain, since lime-stone replaced DRC, and the slightlylower intake would presumably sug-gest less energy was available for gainonce the maintenance requirement wasmet.

Previous studies have suggested theCa:P ratio is insignificant for beef cattleif between 1:1 and 7:1. These resultssupport that conclusion, since there wasno interaction shown between Ca and Plevels with ratios between 1:1 and 5:1.Additionally, P required for maximalgain and bone maintenance for finish-ing yearlings is equal to or less than0.14 % of dietary DM or 15.9 grams/day. The 1996 NRC overestimates Prequired for these animals, and pre-dicts 0.22 % of diet DM or 22.6 g/dP intake. However, high Ca levels maydepress performance if limestone isused and byproducts are fed to mini-mize acidosis-related problems.

1Galen Erickson, graduate student; MarkKlemesrud, research technician; Todd Milton,Assistant Professor, Terry Klopfenstein, Professor,Animal Science, Lincoln.

Use of theNRC Model for

PredictingNutrient

Balances ofFinishing

Cattle

Greg LardyRob McCoyDrew ShainTodd MiltonDennis Brink

Terry Klopfenstein1

The NRC Model is a useful toolfor predicting degradable intakeprotein and metabolizable proteinsupply, requirement, and balancefor feedlot cattle when accurateestimates of intake and proteindegradability are available.

Summary

Trials conducted at the Universityof Nebraska’s Research Feedlot wereused to validate the NRC Beef CattleNutrient Requirements Model. Guide-lines were developed for nutrient val-ues for feedstuffs commonly fed inNebraska feedlots. Generally, the NRCmodel predicted DIP and MP balanceswhich were in agreement with perfor-mance data. The NRC Model generallyunderpredicted feed intake. The NRCmodel correctly predicted DIP defi-ciencies in dry-rolled corn diets whichdid not contain supplemental degrad-able protein. The effective NDF levelof wet corn gluten feed appears to behigher than that of dry-rolled corn. TheNRC model is a useful tool for predict-ing DIP and MP balances for finishing


cattle when accurate estimates of pro-tein degradabilities and intake areavailable.

Introduction

Recently, the National ResearchCouncil (NRC) released the latest ver-sion of the Nutrient Requirements ofBeef Cattle. One of the most significantchanges is the move from expressingprotein requirements on a crude protein(CP) basis to a system which usesdegraded intake protein (DIP) andmetabolizable protein (MP). Proteindegraded in the rumen and available foruse by the rumen microbes is referredto as DIP. MP is the protein utilizedby the host animal and is the sum ofthe digestible bacterial protein pro-duced in the rumen and the digestibleundegraded intake protein (UIP) fromthe feedstuffs consumed. While crudeprotein systems incorrectly assume allfeedstuffs have similar ruminal CPdegrabilities, the NRC Model allowsthe user to enter CP degradabilities foreach feedstuff in the ration.

In order for the NRC model to accu-rately predict nutrient supply to theanimal, accurate estimates of digest-ibility, intake and ruminal proteindegradability are necessary. Our objec-tives were to: 1) report proteindegradabilities for feedstuffs commonlyused in Nebraska; 2) use research trialspreviously conducted at University ofNebraska research facilities to validatethe use of the NRC Model; and 3)present guidelines for successful use ofthe NRC Model for finishing cattle.

Procedure

Research trials previously conductedat the University of Nebraska Agricul-tural Research and Development Cen-ter near Mead, Nebraska were used asvalidation data sets. Diet composition,intake and performance data from eachrespective trial were used as inputs forthe NRC model in order to predict NE

m,

DIP and MP supply, requirement andbalance for various diets. For completedetails regarding diets and cattle man-agement for each trial, refer to pre-vious Nebraska Beef Reports, which

are referenced in the discussion of eachrespective trial.

Results

Table 1 shows suggested model in-puts for effective NDF (eNDF), TDN,CP and ruminal protein degradabilityof several feedstuffs commonly fed inNebraska feedlots. The eNDF level isimportant because the model uses it topredict a diet’s ruminal pH. The pre-dicted pH is used by the model to calcu-

late microbial efficiency, which im-pacts the DIP requirement and MP sup-ply. Low ruminal pH reduces microbialefficiency because the microbial popu-lation expends energy on maintaininginternal ion concentrations rather thanusing the energy for growth, reducingthe DIP requirement and MP supply.

Table 2 shows the effect of urealevel on dry matter intake, gain andfeed efficiency, as well as DIP and MPsupply, requirement and balance for

Table 1. Suggested values for feedstuffs commonly used by Nebraska feedlots.

eNDF TDN CP DIP

Grains

High-moisture corn 0 93 8.4 60Dry corn 0 88 8.45 40Rolled sorghum grain 0 79 10.5 40

Byproducts

Distillers solubles(dry milling) 0 88 28 80

Distillers solubles/steep liquor(wet milling) 0 88 36 80

Wet corn gluten feed 18 88 22 75Sorghum distillers grains + solubles (wet) 18 96 34 40Corn distillers grains + solubles (wet) 18 106 30 40

Protein meals

Soybean meal 0 88 49.9 70Feather meal 0 90 85.8 30Blood meal 0 90 93.8 25

Harvested forages

Corn silage 71 75 7.4 75Alfalfa hay 100 60 16 82Brome hay, mid bloom 100 66 14.4 84Alfalfa hay, early vegetative 100 74 30 93Alfalfa hay, late vegetative 100 67 20.3 85Prairie haya 100 49 6.8 80Prairie haya 100 53 7.7 75aMatch to nearest CP value.

Table 2. Effect of urea level on intake, gain, feed efficiency and DIP and MP supply, requirementand balance for finishing yearlings.

Treatment

CP Level 9.7 12 13.5 15Item Urea Level 0 0.88 1.34 1.96

Dry matter intake, lb/day 25.57 26.17 25.72 25.93Daily gain, lba 2.67 2.91 2.86 2.94Feed/gainbc 9.56 8.99 8.98 8.84

Predicted dry matter intake, lb/day 22.1 22.3 22.0 23.7

DIP supply, g 484 763 928 1123DIP requirement, g 795 823 802 807DIP balance, g -311 -60 126 316

MP supply, g 944 974 948 954MP requirement, g 724 753 741 758MP balance, g 220 221 207 196aNo urea versus urea treatments, P<.01.bNo urea versus urea treatments, P<.05.cFeed/gain was analyzed as gain/feed. Feed/gain is the reciprocal of gain/feed.



finishing yearlings fed a dry rolled corn-based finishing diet (1995 NebraskaBeef Report, pp. 21-22). Gain and feedefficiency were improved by providingsupplemental DIP from urea. The NRCmodel predicted a slight DIP deficiencywith the 12% CP level. However, noimprovements in gain or efficiency werenoted when diets containing more than12% CP were fed. Metabolizable pro-tein balances were positive for all diets,but the NRC model assumes DIP defi-ciencies will be met when it calculatesMP supply. Due to the deficiencies inDIP, the MP supply with the 9.7% CPdiet would be reduced by 199 g assum-ing no additional recycling. This wouldstill be adequate MP for the midpoint ofthe trial. The cattle may have beendeficient in MP during the first half ofthe trial, although the model does notpredict a deficiency. Deficiencies inDIP can also reduce ruminal fermenta-tion of carbohydrate, reducing energyavailable to the animal. Because theruminant has the ability to recycle ni-trogen, excess undegraded intake pro-tein (UIP) in the diet may substitute tosome degree for deficiencies in DIP.This may explain why no advantages infinishing performance were noteddiets contained greater than 12% CP.Excess DIP, however, cannot substi-tute for deficiencies in MP.

The NRC model underestimated drymatter intake of these finishing year-lings by approximately 3 lbs (Table 2).Accurate estimates of intake are a criti-cal input for successful use of the model.In general, the NRC model intake pre-diction equations tend to underesti-mate intake for finishing yearlings, aswell as that of calf-feds, early in thefinishing period. When no informationabout historical performance is avail-able for a particular situation, we rec-ommend using dry matter intakes equalto 3.0% of body weight when the fin-isher diet is first fed for both finishingcalves and yearlings. This will be equalto approximately 20 pounds of drymatter intake for finishing calves and25 pounds for finishing yearlings. In-takes don’t vary markedly on the fin-isher diet from early to late in the feedingperiod. However, if historical intakeestimates for a particular class of cattle

are available, use them instead.Table 3 shows the effect of supple-

mental source of CP on finishing per-formance and DIP and MP supply,requirement and balance for finishingcalves. Control and high-lysine cornwere dry rolled and supplemented withurea, soybean meal or feather meal(1994 Nebraska Beef Report, pp. 30-32). No protein supplement by corntype interactions were detected (P>.15)so data were pooled across corn type.Over the entire trial, the NRC model

predicted intake similar to actual drymatter intake. Daily gain and feed effi-ciency were improved with the additionof soybean meal and feather meal com-pared to urea alone. Over the entiretrial, the NRC model predicted MP wasadequate for all treatments, while DIPwas slightly deficient for the soybeanmeal and feather meal supplementeddiets. It is possible for excess UIP in thediet to meet DIP deficiencies throughrecycling. For the first 63 days of thefinishing period, the NRC model pre-

Table 3. Effect of supplemental protein source on dry matter intake, gain and feed efficiency andDIP and MP supply, requirement and balance for finishing calves.

Finishing Period

Treatmenta

Item U SBM/U FM/U

Dry matter intake, lb/day 19.62 19.43 19.29Daily gainb, lb 2.88 2.97 2.97Feed/gaincd 6.80 6.54 6.49

Predicted dry matter intake lb/day 19.99 19.35 19.45

DIP supply 640 600 590DIP requirement 640 630 630DIP balance 0 -30 -40

MP supply 760 860 840MP requirement 720 720 720MP balance 40 140 120

First 63 Days

Predicted dry matter intake (lb/day) 17.01 16.81 16.99

Actual dry matter intake (lb/day) 21.20 20.60 20.96

DIP supply (g/day) 689 658 638DIP requirement (g/day) 665 653 657DIP balance (g/day) 24 5 -19

MP supply (g/day) 787 882 875MP requirement (g/day) 834 833 828MP balance (g/day) -47 49 47aU=urea, SBM=soybean meal, FM=feather meal.bU vs average of SBM/U and FM/U (P<.10).cU vs average of SBM/U and FM/U (P<.05).dFeed/gain analyzed as gain/feed. Feed/gain is the reciprocal of gain/feed.

Table 4. Effect of energy and protein source on finishing performance and predicted DM intake,and DIP and MP supply, requirement and balance for finishing calves.

Treatmenta

Item DRC/Urea DRC/EP WCGF WCGF/EP

DM intakeb, lb/day 22.73 22.52 21.67 21.97Daily gain, lb 3.81 3.83 3.72 3.80Feed/gainc 5.96 5.88 5.83 5.78

Predicted DM intake, lb/day 18.37 17.89 17.87 17.94

MP supply, g/day 867 939 848 938MP requirement, g/day 817 820 809 816MP balance, g/day 50 119 39 122

DIP supply, g/day 732 729 814 829DIP requirement, g/day 749 739 834 842DIP balance, g/day -17 -10 -20 -13aDRC=dry rolled corn, EP=escape protein, WCGF=wet corn gluten feed.bDRC vs WCGF (P<.05)cFeed/gain analyzed as gain/feed. Feed/gain is the reciprocal of gain/feed.


dicted the urea diet was deficient in MPwhile the soybean meal and feathermeal diets were adequate. Metaboliz-able protein requirement is higher dur-ing the early part of the finishing periodbecause gains are higher. We believethe response to escape protein occurredin the first two months of the feedingperiod, when relative protein require-ments of calves would be higher.

Table 4 shows the effect of energyand protein sources on performanceand DIP and MP balances for finishingcalves. Dry-rolled corn and wet corngluten feed were fed with and withoutsupplemental UIP in a 2 x 2 factorialtreatment design. Details on calf andyearling feeding management are found

in the 1995 Nebraska Beef Report (pp.28-30). No differences in gain or effi-ciency were noted for either energy orprotein source. The NRC model pre-dicted each diet was slightly deficientin DIP but had adequate MP. The NRCmodel underpredicted intake by approxi-mately 4 lbs. Because of the higherprotein degradability of wet corn glutenfeed, a deficiency in MP may be ex-pected when feeding it. However, me-tabolism research (1997 Nebraska BeefReport, pp. 61-65) indicated ruminalpH is higher when wet corn gluten feedis included in the diet at the expense ofdry rolled corn. The NRC model usesthe eNDF of the diet to adjust microbialefficiency downward when eNDF is

Table 5. Suggested inputs and guidelines for use of the 1996 NRC model.

1. Units and Levels Section.Use only Level 1, unless rates of digestion of all feed fractions are known.

2. Animal Section.Remember that your choice of breed affects maintenance energy requirements.Bos indicus cattle have lower NEm requirements, while dairy and dual purpose breeds have higherrequirements. This is discussed in detail in the textbook accompanying the NRC Model.

3. Management Section.A. Microbial Yield. With growing and finishing diets the model uses the effective NDF values of the

feedstuffs to predict a ruminal pH, which is used to calculate microbial yield or efficiency. Useeffective NDF values listed in Table 1. Do not adjust the microbial yield in the model for cattle fedfinishing diets because the model will do this automatically using effective NDF.

B. Diet NEm and NEg Adjusters. Use these to adjust performance predicted by the NRC Model tomatch the actual closeout performance or pen projected performance. The model may calculateunrealistically high feed efficiency and ADG for calves early in the finishing period. We suggestusing the following adjustments for Diet NEm and NEg. For every 100 lb from the midpoint weight,change both NEm and NEg adjusters by 6 percentage units. For example, if calves are being fed from600 lb to 1200 lb, the midpoint is 900 lb. When the calves weigh 700 lb, set the NEm and NEg

adjusters at 88. At 1100 lb the adjusters would be 112. Use this as a guideline only.C. Additive. Select the proper implant and additive used. The model will adjust predicted DMI and

NEm requirements appropriately for the use of ionophores and implants.D. Do not use the On Pasture feature for growing and finishing cattle which are in a pen-fed situation.

This feature increases NEm requirements to account for the impact of grazing activity on nutrientrequirements.

4. Environment Section.A. Temperature. Because of daily fluctuations in temperature, it is difficult to state a temperature

which the cattle are subjected to. Interactions also exist with other environmental factors which arediscussed below. We recommend using long term average temperatures for a given month orseason at a given location.

B. Wind speed. Caution is needed when using this feature. Because cattle behavior is impacted bywind speed, cattle are not subjected to reported wind speeds. Wind speed is generally measuredby anemometers positioned 10' above ground. Cattle are seldom subjected to these wind speedsbecause they will find ways to minimize the effect of wind on them. We recommend using windspeeds of less than 5 miles per hour in most cases.

C. Hair Depth. Use .25 inches in the summer and .5 inches for winter coats.D. Hide. Use 1 (thin hide) for Bos indicus and dairy breed types, and 2 (average) or 3 (thick) for most

English and Continental breeds.

5. Feeds Section.A. Use the Feed Library (a feature separate from the model) to make global changes to feedstuff

composition. Use the Feed Composition feature to make feed composition changes specific to aration or problem (composition changes made in this manner will be specific to that input file only).

B. When estimates of feed intake are unavailable or unknown, use the NRC estimated intake as aguideline. As a general guideline, use 3% of body weight when the finisher diet is first fed as anestimate of feeding period intake for calves and yearlings.

less than 20%. For diets with greaterthan 20% eNDF, the model makes noadjustment. For each 1% decrease ineNDF from 20%, the model decreasesmicrobial efficiency by 0.29% (begin-ning at 13%). For example, if the dietcontained 5% eNDF (common with agrain based finishing diet containing7.5% roughage), microbial efficiencywould be reduced by 4.35% and wouldbe equal to 8.65% [13%-4.35%]. Bio-logically, the reason for this efficiencyreduction is related to microbial physi-ology in the rumen. When pH drops, themicrobial population spends more en-ergy for maintenance rather than growth.Therefore, microbial protein produc-tion is reduced, resulting in decreases inMP supply, as well as decreases in theamount of DIP required by the mi-crobes.

Table 5 lists the guidelines recom-mended for successful use of the modelwith growing and finishing cattle. Likeany computer program, the model ishighly dependent on user-given inputs.Key areas when considering inputs are:1) Microbial yield; 2) Diet NE

m and NE

gadjusters; and 3) the Environment sec-tion. For finishing diets, leave 13% asthe default value for microbial yield.The model will automatically calculatethe predicted yield. Use the diet NE

m

and NEg adjusters to adjust performanceof the cattle to match projected or ac-tual gain and feed efficiency. The modelis very sensitive to wind speed andtemperature inputs. Consequently, thepredicted energy requirement can fluc-tuate a great deal depending on envi-ronmental inputs.

The NRC model is useful for pre-dicting DIP and MP balance when real-istic estimates of intake and ruminalprotein degradability are available.Without these estimates however, theuser may not get accurate predictions.In general the NRC model tended tounderpredict DM intake of both finish-ing calves and yearlings. If historicalestimates of intakes for a particularclass of cattle are known, they shouldbe used for NRC model calculations.

1Greg Lardy, Rob McCoy, Drew Shain, formergraduate students; Todd Milton, Assistant Professor;Dennis Brink and Terry Klopfenstein, Professors,Animal Science, Lincoln.


Evaluation of 1996 NRC for Protein andPhosphorus Requirements of Finishing Cattle

Galen EricksonTodd Milton

Terry Klopfenstein1

The 1996 NRC computer modeldoes not under-predict the proteinand phosphorus requirement offinishing calves and yearlings

Summary

Two trials were conducted to evalu-ate the 1996 Beef NRC computer modelfor protein and phosphorus require-ments of feedlot cattle. The controlration was formulated for the samelevels of crude protein (13.5%) andphosphorus (0.35%) in both trials; how-ever, supplemental protein was fromurea in Trial 1 and urea, feather mealand blood meal in Trial 2. The bal-anced ration was formulated utilizingthe 1996 NRC. The balanced rationwas changed to effectively meet thechanging requirements for DIP, UIPand P. In Trial 1, gains and efficiencieswere similar between treatments; how-ever, DMI was lower with cattle fed thebalanced ration. In Trial 2, animalperformance was unaffected by dietarytreatment. These results indicate thatthe 1996 NRC model does not under-predict finishing steer protein and Prequirements.

Introduction

In 1996, the NRC beef committeeupdated the requirements for beef cattle.There were numerous advancementsadopted, including a computer modeland a metabolizable protein (MP) sys-tem. The MP system accounts for twodifferent requirements, microbial andanimal, which must be met to optimizeperformance. Each feedstuff is degradedto various degrees in the rumen. For

example, high-moisture corn (HMC) is8 - 10% protein which is 60 % degrad-able in the rumen, whereas dry-rolledcorn (DRC) contains the same amountof crude protein but is only 40 % de-gradable by the ruminal microbes.

Calves have a higher MP require-ment than yearlings. At the same time,calves require less MP at the end of thefinishing period than at the beginning.Therefore, if the diet is to meet therequirements, the diet must change bothbetween yearlings and calves and withintime on feed. This is commonly re-ferred to as “phase feeding.” Under-standing this system allows nutritioniststo more effectively optimize perfor-mance without overfeeding.

Protein requirement can be dividedinto two segments, degradable intakeprotein (DIP), which meets the micro-bial requirement and undegradable in-take protein (UIP), which bypasses therumen and is used by the animal at thesmall intestine in addition to microbialprotein leaving the rumen. Our objec-tive was to evaluate the 1996 NRCguidelines with both calves and year-lings and balance a ration to meet theDIP and UIP requirements while mini-mizing the overfeeding of protein andphosphorus.

Procedure

In Trial 1, 96 crossbred, yearlingsteers (BW = 656 lb, age = 14 mos) wererandomly assigned (8 hd/pen) to eitherthe control ration or the balanced ra-tion. Steers were on feed 147 days fromMay 10 to October 4, 1996 and im-planted with Revalor-S on day 0 andday 84. Cattle were adapted to the fin-isher diet with four step diets contain-ing 45, 35, 25 and 15 % alfalfa hay fedfor 3, 4, 7 and 7 days respectively. Thecontrol ration (Table 1) was formulatedto provide 13.5 % crude protein and0.35 % phosphorus (P), with all supple-

mental protein from urea. The balancedration was formulated using the 1996NRC model (predicted final wt = 1200,50 % Br X 50 % Cont, ADG = 3.7 lbs/d) to meet and not exceed the DIPrequirement and minimize excess UIPin the diet. Since protein from HMC ismore degradable in the rumen, and therequirement for DIP as a portion of MPrequired is greater for yearlings, theDRC was replaced with HMC in thebalanced ration to minimize overfeed-ing of UIP. Likewise since corn con-tains 0.25 to 0.30% P, and therequirement is 0.23 % P for 750 lbyearlings, the balanced ration containedenough corn bran (0.10 % P) to meet,but not exceed, the P requirement pre-dicted by the NRC model. Since the Prequirement changes with days on feed,various levels of corn bran were fed for28, 28 and 58 days, respectively.

In Trial 2, 96 crossbred steer calves(BW = 541 lb, age = 8 mos) wererandomly assigned (8 hd/pen) and fedfor 193 days from November 8, 1996 toMay 20,1997. Steers were implanted onday 1 and day 97 with Revalor-S. Cattlewere adapted to finisher diets (7.5 %alfalfa) similar to Trial 1 except eachstep ration was fed for 7 days. Thecontrol ration was formulated to pro-vide 0.35 % P and 13.5 % crude proteinjust as Trial 1; however, supplementalprotein was from urea, 1.4 % feathermeal and 0.2 % blood meal on a DM-basis, supplemented for escape proteinthroughout the 193 days. The balancedration was formulated similarly to Trial1 (predicted final wt = 1200 lbs, 50 % BrX 50 % Cont, ADG = 3.9 lbs/d). Table1, however, illustrates the change inrequirement with calves as predicted bythe NRC. The first seven finisher dietswere fed for 14 days each and finisher 8was fed until slaughter. Since calvesinitially require less DIP as a percent-age of total protein fed, DRC was usedand gradually switched over to HMC by


finisher 7. The P requirement also de-creases with increasing weight of theanimal, so HMC was gradually replacedwith corn bran to prevent overfeedingof P.

Initial weights used for both trialswere an average of two consecutiveweights at the initiation of the trialfollowing a 5-day limit-feeding period.At slaughter, hot carcass weights andliver scores were recorded. Qualitygrade, yield grade and fat thickness atthe 12th rib were recorded following a48 hr. chill. Final weights were calcu-lated as hot carcass weight divided by acommon dressing percentage (62).

Results

In Trial 1, steers fed the balancedration had lower (P<.01) DMI than steersfed the control ration (Table 2). Gainsand feed efficiency of steers fed thebalanced ration were similar to controlsteers, despite feeding a diet that was2% units lower in crude protein andcontained no supplemental P. Carcasstraits were also unaffected by dietarytreatment.

In Trial 2, calves fed the balancedration had similar DMI, ADG and feedefficiency as control animals. Initially,calves on the balanced ration were fed

Table 1. Diet composition (% of DM).

Trial I — Yearlings Trial II — Calves

Itema Contr. Fin 1 Fin 2 Fin 3 Contr. Fin 1 Fin 2 Fin 3 Fin 4 Fin 5 Fin 6 Fin 7 Fin 8

DRC 81.3 82.5 82.5 82.5 82.5 82.5 59.5 35.0 4.5HMC 67.4 64.6 61.4 16.5 36.5 61.0 57.5C.bran 17.2 19.9 23.1 6.5 11.0 17.0 25.0Liq-32 6.2 5.0molasses 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0fat 3.0 3.0 3.0Alfalfa 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5Suppl. 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0

urea 0.52 0.76 0.76 0.76 0.29 0.83 0.88 0.91 0.96 0.87 0.75 0.62 0.60FMb 1.40 1.60 1.15 0.75 0.18BMc 0.20 0.20 0.14 0.10 0.02dical P 0.48 0.47 0.10 0.04

CP (%) 13.6 11.2 11.9 11.5 13.4 12.7 12.4 12.1 11.7 11.5 11.2 10.8 10.9UIP (%)d 4.48 3.67 3.67 3.67 5.16 5.51 5.23 4.99 4.64 4.11 3.68 3.11 3.02P (%) 0.34 0.24 0.24 0.22 0.35 0.26 0.25 0.24 0.24 0.23 0.22 0.21 0.20

aDry-rolled corn, high-moisture corn, corn bran and liquid supplement.

bFeather meal.cBlood meal.dBalanced finishers for Trial 1 unavoidably contained more UIP than required.

Table 2. Performance of finishing yearlings and calves.

Trial 1 — Yearlings Trial II — Calves

Item Control Balanced SE P< Control Balanced SE P<

Initial wt. 652 660 2.8 .12 539 542 .63 .01Final wt. 1249 1249 9.8 .99 1245 1247 10.8 .59DM Intake 26.2 25.0 .20 .01 20.6 20.5 .25 .77ADG 4.06 4.01 .06 .60 3.66 3.65 .06 .74Feed/gain a 6.45 6.21 .15 5.72 5.64 .61

HCW b 774 774 6.1 .99 769 774 6.7 .59QG c 18.5 18.1 .25 .30 18.5 18.3 .10 .17Fat depth 0.52 0.51 .01 .70 0.55 0.53 .01 .14

aAnalyzed as gain to feed, the reciprocal of feed to gain.bHot carcass weight.cQuality grade where 18 = Select+, 19 = Choice-.

more escape protein (UIP) and gainswere numerically greater than controlsteers. Dry matter intake did varybetween treatments during each fin-ishing phase.

Results indicate the 1996 NRCrequirement system is an effective toolto manipulate protein feeding regimensin the feedlot without compromisinganimal performance. Additionally,“phase feeding” matches dietary sup-ply with changes in animal nutrientrequirements with time on feed. How-ever, this system does require formula-tion of multiple finisher rations,increasing feed delivery managementand supplement inventory.

Phosphorus is an expensive nutrientand is not as critical to supplement(1998 Beef Report, pp 78) in feedlotdiets as is commonly believed, espe-cially since energy sources are nor-mally greater than 0.25 % P. Animalperformance for both calves and year-lings was unaffected by decreasing Plevels below 0.25 %. Therefore, weconclude P supplementation is unnec-essary because of the monetary andpotential environmental cost.

1 Galen Erickson, graduate student, ToddMilton, Assistant Professor, Terry Klopfenstein,Professor, Animal Science, Lincoln.


Nutrient Balance of Nitrogen, Organic Matter,Phosphorus and Sulfur in the Feedlot

Galen EricksonTerry Klopfenstein

Dan WaltersGary Lesoing1

Decreasing protein and phos-phorus intake to requirements pre-dicted by 1996 NRC maintainedanimal performance, decreased ni-trogen and phosphorus excretion,and improved waste characteris-tics.

Summary

Ninety-six crossbred yearling steers(656 lb) were assigned to either control(CON) or balanced (BAL) treatments.Steers were fed for 135 days in 12waste-management pens with runoffcollection basins. Control diet con-sisted of a DRC, 7.5 % roughage fin-isher formulated for 13.5 % proteinand 0.35 % phosphorus. Balanced dietwas formulated using the 1996 NRCmodel to meet the animal’s protein(11.5%) and phosphorus (0.22%) re-quirements. Gains were unaffected andfeed efficiency tended to improve byfeeding the BAL diet. Nitrogen and Pexcretion were lower with BAL steerscompared with CON steers. Conse-quently, the manure’s N:P ratio wasimproved relative to crop needs from1.9:1 to 3:1 for CON and BAL treat-ments respectively. Feeding at theanimal’s requirement for protein and Pdecreases N and P excretion and im-proves waste characteristics withoutcompromising animal performance.

Introduction

With the concentration of the feed-lot industry into fewer acres and fewerproducers, waste management is

becoming an increasingly importantissue. Feedlot design has advanced tohandle the nutrient concentration inthese feedlots, particularly surfacerunoff and leaching. From a cost per-spective, minimizing total manure pro-duction and decreasing removal time isadvantageous. Since manure should beused as a crop fertilizer in feedlot areas,concentration of nitrogen (N) and phos-phorus (P) is critical, as crops require a5:1 N to P ratio.

When manure is used as a fertilizer,either excess P is applied to the landbase or extra N needs to be applied tooptimize crop yields, since manure typi-cally contains a 2:1 N to P ratio or less.The reason the ratio is typically muchlower than 5:1 is partially due to 50 - 70% of the N volatilizing from the penafter excretion. Phosphorus does notvolatilize. Increasing N or decreasing Pwill add value to the manure relative tocrop needs. From a land base require-ment perspective, decreasing total Nand P excretion would be the mostadvantageous.

In 1996, the NRC beef committeeadopted the metabolizable protein sys-tem for evaluation of animal require-ments. This system allows nutritioniststo match dietary inputs with require-ments more accurately than the previ-ous crude protein system.

The objective of this study was todetermine effects of minimizing over-feeding of protein and phosphorus onwaste management in the feedlot.

Procedure

Ninety-six crossbred yearlings (BW= 656 lb) were used in 12 waste man-agement pens (8 hd/pen). Soil in penswas core sampled (0 to 6 inches) beforethe trial to estimate nutrient concentra-tion on the pen surface. The animalswere then fed for 135 days and pens

cleaned after the trial. Manure wassampled during removal and pen soilsamples collected to estimate nutrientbalance. Soil sampling allows adjust-ment for inevitable cleaning differencesbetween pens. The pens also containedrunoff collection basins to determinetotal runoff from pens on different treat-ments. Due to pen design, two pensdrain into one pond; therefore dietarytreatments were assigned in blocks oftwo pens. All samples including feedand feed refusals were analyzed for N,OM, P and S.

Two dietary treatments included thecontrol ration (CON), 13.5 % proteinand 0.354 % P, and balanced ration(BAL) which minimized protein and Pfed to meet, and not exceed, the require-ments predicted by the 1996 NRC, 11.5% protein and 0.22 % P. Control rationincluded (DM-basis): 81.3 % dry-rolledcorn (DRC), 7.5 % alfalfa, 6.2 % molas-ses with urea and 5.0 % dry supplement.Balanced ration included: 61.4 to 67.4% high-moisture corn (HMC), 17.2 to23.1 % corn bran, 7.5 % alfalfa, 3.0 %fat and 5.0 % supplement. Since HMCreplaced DRC in the balanced ration,more protein was rumen degradable;therefore less urea was needed to meetthe degradable intake protein (DIP) re-quirement. Corn bran was also added todecrease the P level to the predictedrequirement. Three rations were fed insteps with increasing levels of cornbran since the P required decreases withtime on feed.

Results

Animal weights, gains and efficien-cies were similar between CON andBAL steers (Table 1). Dry matter intakeand organic matter (OM) intake weregreater (P<.01) for CON fed steers.Since BAL contained corn bran to lowerP intake, OM excretion was increased


steers. More N was removed from BALpens, even though N excretion was less.Since more OM was excreted due to thecorn bran, more N was trapped on thepen surface with the BAL treatment ascompared to CON. This is shown inpercentage of excreted N volatilized asammonia, which was 65.4% for BALpens compared to 74.2 % for CON pens.

Phosphorus intake was reduced from12.5 lbs/hd to 7.9 lbs/hd for the 135-daytrial for both diets (Table 3). The re-duced intake leads directly to a reduc-tion in P excretion, since retention isdependent on retained protein and gain.Similar amounts of P were removed atcleaning from both diets. The BALcattle excreted less P, suggesting P re-moved in manure should also be less;however, more P was removed from thepen than was present at the start of thetrial, illustrated by the soil core bal-ance. Since P is not volatile, the P notaccounted for suggests discrepanciesexist between samples and what iseither on the soil surface of the pen or inthe manure at cleaning.

Sulfur intake and excretion werereduced (P<.01) for BAL steers com-pared to CON (Table 3). However, moreS was removed in the manure than wasexcreted in the BAL pens. The corebalances suggest more OM, N, P and Swere removed at cleaning than werepresent before the trial in BAL pens.Less than 5 % of excreted S in CONpens and 11 % in BAL pens was pre-sumably volatilized, suggesting totalreduced sulfur and other volatile sulfurcompounds are not significant.

Reducing protein and phosphoruslevels maintained animal performanceand decreased N and P excretion. Theincrease in OM excretion did allowmore OM and N to be removed eventhough N excretion was reduced. TheN:P ratio in the manure was increasedfrom 1.9:1 to 3:1 for CON and BALtreatments respectively.

1 Galen Erickson, graduate student, TerryKlopfenstein, Professor, Animal Science, DanWalters, Associate Professor, Agronomy, GaryLesoing, Research Assistant Professor, Center forSustainable Agricultural Systems, Lincoln.

Table 1. Performance of yearling steers by treatment.

Treatment

Item Control Balanced SE P<

Initial weight 652 660 2.8 .12Final weight 1249 1249 9.8 .99DM Intake 26.2 25.0 .2 .01ADG 4.06 4.01 .06 .60Feed/gaina 6.45 6.21 .15

aAnalyzed as gain to feed, the reciprocal of feed to gain.

Table 2. Organic matter (OM) and nitrogen (N) balance.

Organic matter Nitrogen

Item Control Balanced SE P < Control Balanced SE P <

(lbs/hd/day)Input 25.2 23.3 .21 .01 0.56 0.47 .004 .001Retentiona 0.06 0.06 .0005 .26Excretionb,c 5.15 7.16 .06 .001 0.50 0.42 .004 .001

(lbs/hd)Excreted 703 941 7.8 .001 66.3 54.6 .56 .001Manure 242 404 9.6 .001 12.6 19.7 .52 .001Soild 7.9 -86 22.6 .05 2.07 -2.83 1.66 .10Runoff 61 47 6.2 .20 2.47 2.07 .29 .40Volatilizede 393 576 28.8 .01 49.2 35.7 1.77 .01% volatilized 56 61 74 65

aN retention based on ADG, NRC equation for retained energy and retained protein.bOM excretion calculated as 20.7 % indigestibility for control and 29.9 % for balanced.cN excretion calculated as intake minus retention.dSoil value is from core balance on pen surface before and after trial; negative values suggest removal ofnutrient present before trial.eVolatilized calculated as excretion minus manure minus soil minus runoff.

Table 3. Phosphorus (P) and sulfur (S) balance.

Phosphorus Sulfur

Item Control Balanced SE P < Control Balanced SE P <

(lbs/hd)Intake 12.52 7.90 .08 .001 6.46 5.23 .04 .001Retentiona,b 2.05 2.03 .02 .30 0.51 0.50 .004 .27Excretedc 10.47 5.87 .07 .001 5.96 4.73 .04 .001Manure 6.77 6.49 .28 .50 3.41 5.48 .29 .01Soild -1.25 -2.99 .78 .20 -0.13 -3.61 1.17 .10Runoff 1.75 1.49 .08 .10 2.37 2.33 .24 .90Differencee 3.21 0.89 .86 .12 0.30 0.53 1.22 .90

aP retention based on NRC retained protein, 3.9 g / 100 g protein gain.bS retention based on NRC requirement for sulfur amino acids, 4 g SAA / 100 g protein gain.cP and S excretion calculated as intake minus retention.dSoil value is from core balance on pen surface before and after trial; negative values suggest removal ofnutrient present before trial.eP and S difference calculated as excretion minus manure minus soil minus runoff.

(P<.01) compared with CON (Table 2).Organic matter removed in manure wasincreased in BAL pens, due to moreexcreted and more removed from pensurface. Estimates of OM volatilizationor loss was 393 lbs/hd for CON and 576lbs/hd for BAL. When expressed aspercent volatilization, approximately

the same amount of OM was lost fromeach treatment, 56 % and 61 % for-CON and BAL pens, respectively.

Nitrogen intake was reduced withBAL treatment (Table 2). Since animalperformance was similar, retained pro-tein and N were similar, leading to lessN excretion by BAL steers than CON


Rick KoelschGary Lesoing1

Nitrogen and phosphorus inputsin excess of managed outputs onmany Nebraska feedlots is a driv-ing force behind the environmen-tal challenges faced by the industry.

Summary

A balance between the nutrientinputs and the managed nutrient out-puts balance was constructed for 16Nebraska feedlots to provide insight topotential environmental risks. Sub-stantial nitrogen and phosphorusimbalances were observed for manyparticipating feedlots. Size of the live-stock operation and the degree ofintegration of livestock with a crop-ping operations provided only limitedexplanation concerning nutrientbalance variations observed amongthe feedlots. Substantially improvednutrient balances were achieved bythose feedlots marketing manure nutri-ents to off-farm customers. A “sus-tainable” nutrient balance appearspossible for larger feedlots activelymarketing manure nutrients.

Introduction

Nitrogen and phosphorus losses tosurface and groundwater are criticalwater quality issues associated withlivestock manure. In Nebraska, live-stock and poultry excrete approximately320,000,000 pounds of nitrogen and230,000,000 pounds of phosphorus an-nually. A 1995 GAO report to the UnitedStates Senate suggested manure wasthe source of 37% of all nitrogen and65% of all phosphorus into watershedsin the central states, including Nebraska.

An underlying cause to the environ-mental problems associated with live-stock production is the accumulation ofnutrients on livestock farms. A largefraction of nutrients consumed by ani-

mals does not leave the farm as meat.Klopfenstein has previously reportedyearling cattle retain only 10.4% and18.5% of the nitrogen and phosphorusfed, respectively. Most nutrients fed toanimals remain on the farm in manure.

The intent of this study is to definethe nutrient balance on Nebraska live-stock operations. The study also at-tempts to identify characteristics ormanagement practices minimizing theaccumulation of nutrients on farm.

Procedure

An accounting of nutrient inputs (pur-chased feed, fertilizer, animals, bio-logically fixed nitrogen and nitrates inirrigation water) and managed nutrientoutputs (animals, crops and other prod-ucts moved off-farm) was completedfor 16 cattle feedlot operations (Figure1). Changes in farm inventory wereincluded in the analysis. The account-ing period was for one year (1995 forfour feedlots and 1996 for 12 feedlots).The degree of imbalance was estimatedbased upon differences in inputs, man-aged outputs and inventory changes.The calculated imbalance in nutrientscan either be lost to the environment(nitrate leaching to groundwater, nitro-gen in surface water runoff or ammoniavolatilization) or added to soil storagemechanisms (increasing potential for

phosphorus losses in surface runoff).When available, measured nutrient

concentrations values for individualfeedlot nutrient inputs and outputs wereused. Generally, a nutrient analysis wasavailable for purchased feeds and mar-keted manure and sometimes for cropssold. Literature values were used forother nutrient inputs and outputs. Feedvalues from the 1996 NRC NutrientRequirements of Beef Cattle were usedfor crops and feeds with no individualfarm nutrient analysis.

Results

The nutrient balance is defined(Table 1) for two integrated crop andlivestock operations (Farms 1 and 2)and two predominantly cattle feedlotoperations (Farms 3 and 4). The magni-tude of the nitrogen (41 tons to 2,180tons per year) and phosphorus (-4 to+280 tons per year) accumulation onthese four farms was significant. Farms1 and 2 exhibited a smaller relativenitrogen imbalance (approximately 50%of inputs) and a negative or neutralphosphorus balance. Both have a sub-stantial land base relative to the animalnumbers. Farms 3 and 4 relative nutri-ent imbalances were larger (approxi-mately 75% of nitrogen inputs and 60%of phosphorus inputs). The relative re-liance on home-grown feeds (Farms 1

Nutrient Balance on Nebraska Feedlots

Imbalance

Inputs

Feed

Animals

Fertilizer

Legumes

Irrigation

Cattle

Crops

Manure

ManagedOutputs

(losses to environment oradditions to soil storage)

Figure 1. Balance Between Nutrient Inputs and Managed Outputs for a Feedlot.


and 2) versus purchased feeds (Farms 3and 4) is a primary difference betweenthese four operations.

From a water quality perspective,phosphorus balance (phosphorus is gen-erally conserved by the manure man-agement systems) provides a betterindication as to when a sustainable nu-trient balance has been achieved. Sub-stantial losses of ammonia nitrogen byvolatilization often mask when a bal-ance is achieved. In addition, differ-ences in volatilization losses betweenfarms make nitrogen balance compari-sons difficult.

The value of exporting manure nu-trients to off-farm customers is illus-trated in Table 2. As illustrated in Table1 the nutrient balance for farms 3 and 4assumes no export of manure nutrientsfrom these farms. In fact, both farmsactively market manure nutrients, sub-stantially improving the nutrient bal-ance of both. Nitrogen imbalance hasbeen reduced, but not eliminated. Theremaining nitrogen imbalance is prob-ably due to ammonia volatilizationlosses to the atmosphere from the feed-lot surface, manure storage (farm 4only) and composting (farm 3 only).The phosphorus imbalance has beeneliminated for farm 3 and substantiallyreduced for farm 4. Marketing of ma-nure nutrients to off-farm customersappears to have achieved a sustainablenutrient balance for farm 3 and substan-tially improved the sustainability offarm 4.

A nutrient balance, including anytransfer of manure to off-farm custom-ers, was completed for a total of 16cattle feedlots. The relative imbalancemeasured as a percentage of inputs ofnitrogen and phosphorus, is sum-marized in Figure 2. The increasingimbalance with feedlot size observedin Table 1 is less evident in Figure 2.The largest imbalances of nitrogenwere observed for several smallerfeedlots. The phosphorus imbalanceshows some advantage for several ofthe smaller feedlots. A negative phos-phorus imbalance was observed forseveral of the smaller feedlots.

The degree of integration of cropand livestock enterprises is often

Table 1. Nitrogen and phosphorus balance for four Nebraska feedlots.a

Farm 1 Farm 2 Farm 3 Farm 4

Farm Characteristics

Animal Units (1000 lb.)b: 540 3770 4330 20,650

Crop Acres Per Animal Unit: 1.7 0.4 0.0 0.1

Nitrogen (tons/year)

Inputs 94 130 516 2852Managed Outputs -46 -68 -135 -639Inventory Change -8 0 0 -30

N Balance ...tons 41 62 381 2,183% 47% 48% 74% 77%

Phosphorus (tons/year)

Inputs 6 18 94 459Managed Outputs -8 -19 -37 -168Inventory Change -2 0 0 -9

P Balance ...tons -4 -1 57 280% -98% -7% 61% 62%

aThis nutrient balance assumes no export of manure nutrients to off-farm customers. Any corrections tothis assumption will be made in Table 3.bAnimal units represents the average animal capacity of a feedlot times the average animal weight dividedby 1,000. A 2,000 head feedlot average capacity with an average animal weight of 950 pounds represents1,900 animal units (2,000 X 950 / 1,000 = 1,900).

Table 2. Nutrient balance for a 4,500 head feedlot with no land base and 20,000 head feedlot withlimited land base with and without off-farm marketing of manure nutrients.

Is Marketing of Manure Nutrients ToOff-Farm Customers Credited?

Farm 3 Farm 4

NO YES NO YES

Nitrogen Imbalancea 381 t/yr. 316 t/yr. 2,183 t/yr. 1,465 t/yr.(74%) (61%) (77%) (52%)

Phosphorus Imbalancea 57 t/yr. -1 t/yr. 280 t/yr. 156 t/yr.(76%) (-1%) (62%) 35%

aTons of nutrient per year (percent of total nutrient inputs).

(Continued on next page)Figure 2. Nutrient balance versus size of livestock facility for 16 Nebraska feedlots.

100

80

60

40

20

0

-20

-40

-60

-80

-100

Nut

rient

Bal

ance

(%

)

Phosphorus

Nitrogen

0 5,000 10,000 15,000 20,000 25,000

Livestock Operation Size (1,000 lb. animal units)


animal density. Farms with a signifi-cant land base have greater potential forexporting of phosphorus as crops mar-keted off farm.

Substantial variation in nutrient bal-ance exists between farms. Size of live-stock operation (Figure 2) and degree ofintegration of the livestock operationwith a crop operation (Figure 3) provideonly limited explanation of this varia-tion. The role other farm characteristicsor management practices play in deter-mining the variation in nutrient balancerequires additional evaluation.

1Rick Koelsch, Assistant Professor, BiologicalSystems Engineering and Animal Science, Lincoln;Gary Lesoing, Research Assistant Professor, Centerfor Sustainable Agricultural Systems, Lincoln.

Figure 3. Nutrient balance versus crop land to animal density for 16 Nebraska feedlots.

considered an indicator of the relativepotential for environmental problems.For the 16 participating farms, the ni-trogen imbalance showed little change

for greater animal densities (lower cropacres to animal units, Figure 3). How-ever, the phosphorus imbalance tendedto be smaller or negative for lower

100

80

60

40

20

0

-20

-40

-60

-80

-100

Phosphorus

Nitrogen

0.00 1.00 2.00 3.00 4.00

Animal Density (Crop Acres per Animal Unit)

Nut

rient

Bal

ance

(%

)

In Situ Method for Estimating ForageProtein Degradability

Ryan MassGreg LardyRick Grant

Terry Klopfenstein1

A method of estimating forageprotein degradability is available.In situ neutral detergent fiber nitro-gen provides information neces-sary to calculate metabolizableprotein supplied to cattle consum-ing forage.

Summary

Four experiments including vegeta-tive and dormant forages tested modi-fications of the in situ neutral detergentfiber nitrogen (NDFN) method of esti-mating forage undegraded intake pro-tein (UIP). Experiments 1, 2 and 3tested bag size, closure, rinsing, den-sity, and reflux conditions. None of themodifications affected in situ NDFNcontent. Experiment 4 compared rates

of in situ NDFN digestion calculatedwith or without correction forundegradability. A close relationshipexists between rates calculated by thetwo methods. Modifications make theimproved in situ NDFN method a moredesirable means of estimating forageUIP than the standard method.

Introduction

Metabolizable protein, the proteinabsorbed by the animal, equals the sumof digestible microbial protein andundegraded intake protein (UIP). Infor-mation about the ruminal degradabilityof dietary protein is necessary to de-scribe the contribution it makes to boththe microbial protein and UIP. Esti-mates of DIP and UIP are needed tocalculate MP using the 1996 NRC com-puter software. However, few estimatesof forage UIP are available.

Previous research (1997 NebraskaBeef Report, pp. 38-39) indicates neu-tral detergent fiber nitrogen (NDFN) isan effective method of estimating for-

age UIP. Our objectives were: 1) to testthe effect of modifications of the methodon in situ NDFN content; and 2) toexamine the relationship between ratesof in situ NDFN digestion calculatedwith or without an undegraded fraction.

Procedure

All three experiments were con-ducted under similar conditions. Eachexperiment consisted of one 16- hourincubation in a ruminally fistulated steerfed smooth bromegrass hay (8% CP) at1.8% of body weight. Smooth brome-grass hay was incubated in every in situbag. Four bags were incubated for eachlevel of each factor. Estimates of UIP(mg NDFN/g sample incubated) werecalculated and each experiment wasanalyzed separately.

Experiment 1 tested modificationsof a standard in situ method. Factorstested were (standard conditions listedfirst): in situ bag size (10 × 20 cm vs 5× 10 cm), degree of post-in situ handrinsing (45 min vs 15 min), bag closure



method (rubber band around a #8 rub-ber stopper vs heat-sealing) and NDFmethod (individual refluxing ofsubsampled residue versus bulk reflux-ing of the bag containing its residue).The amount of sample incubated in thesmall bags was reduced (1.25 g) inorder to maintain the same sample/bagsurface area ratio as the large bags. Thesame number of rubber stoppers wasplaced in each mesh bag in order toensure similar weights for each. A bulkrefluxing apparatus was used for neu-tral detergent extraction (Ankom, Inc.,Fairport, NY).

Experiment 2 was conducted usingmodifications tested in Experiment 1.All in situ bags were 5 × 10 cm andcontained 1.25 g of sample. Bags werehand-rinsed for 15 min immediatelyafter the incubation. The bags wereheat-sealed and refluxed in neutral de-tergent solution in the bulk apparatus.The first factor tested a modification ofthe standard incubation conditions. Insitu bags were incubated in the steer attwo densities (20 bags/mesh bag versus50 bags/mesh bag). Two mesh bagswere incubated for each density. Thesecond factor concerned the refluxingconditions. Use of the bulk reflux appa-ratus required placement of the in situbags in a cylindrical rack. The rackconsists of eight removable dishes. Eachdish is capable of holding three in situbags, for a total of 24 bags possible ineach reflux. Dishes were stacked verti-cally and held by a metal rod. Wehypothesized dish position would notaffect NDFN content. The top and bot-tom two racks were used as the twolevels of the second experimental fac-tor. Twelve bags from each mesh bagdensity (three per replication) were cho-sen randomly and allotted randomly toeither the top or bottom level of the twoconducted refluxes.

Experiment 3 was conducted usingmodifications tested in Experiment 2.Small, heat-sealed in situ bags (5 ×10cm) were incubated at a density of 50bags/mesh bag. Bags contained 1.25 gof sample and were rinsed after incuba-tion for 15 min. Bags were assignedrandomly to dishes in the bulk refluxrack. Factors tested were time of NDFreflux (40 min vs 70 min) and extent of

post-NDF bag rinsing (.5 L water/bagvs 1 L water/bag).

Experiment 4 was conducted to de-scribe the effect of correcting the rate ofin situ NDFN digestion (k

d) for an

undegradable fraction. Three sets offorage samples were incubated togetherin the rumen and were collected usingeither esophageally or ruminally fis-tulated animals. Samples were collectedfrom animals grazing the followingforages (number of samples taken inparentheses): cornstalks (n=24), grow-ing cool-season grasses (n=36) andwinter native range ( n=24).

All of Experiment 3’s incubationmodifications were used. Small bags (5x 10 cm) were heat-sealed and incu-bated at a density of 50 bags/mesh bag.Bags were refluxed in neutral detergentsolution in groups of 24. Each samplewas incubated for 2, 12 or 96 hours.Incubations were replicated three times.Two different regression equations werecalculated using the natural logarithmof mg NDFN/g of sample incubated.The slope of the regression equationequals k

d. The first k

d was calculated

using bags incubated for 2 and 12 hours.This method assumes that NDFN is100% degradable in the rumen. Thesecond k

d was calculated by subtracting

the 96 hour (96NDFN) value from boththe 2 and 12 hour values. These newvalues were used to calculate a separatek

d. The second method assumes that the

NDFN pool has reached its extent ofruminal degradation by 96 hours. Re-gression analysis was used to describethe relationship between the two calcu-lations.

Results

No differences (P>.05) in 16-hour insitu NDFN content were observed be-tween bag sizes. These results agreewith previous research, which indicatedforage DM digestibility is unaffectedby bag size as long as the sample size/bag surface area ratio remains constant.

Rinsing in situ bags after incubationis necessary for the removal of rumenmicrobes from the bag and its residue.It was hypothesized that less rinsingwould be necessary if NDFN was theUIP pool. Previous results indicate

neutral detergent solution refluxremoves attached microbes (1997Nebraska Beef Report, pp. 38-39). Nodifferences (P>.05) were observed in16-hour in situ NDFN content betweenbags rinsed for 45 versus 15 min.Reduction in the time spent washingmakes the method more efficient andmight reduce washout of small par-ticles.

The final two factors in Experiment1 (method of bag closure and NDFmethod) were included to test the effi-cacy of bulk refluxing of bags. It isnecessary to heat-seal the bags whenreflux is conducted directly on the bagand its residue. No effect (P>.05) ofeither factor was found. The results ofExperiment 1 indicate the in situ NDFNprocedure can be conducted usingsmaller, heat-sealed bags rinsed for 15min after incubation and refluxed inbulk. These modifications will decreasethe amount of labor needed to conductthe procedure.

The standard in situ method allowsno more than 20 in situ bags in one meshbag and up to 6 mesh bags in oneruminal incubation. However, the useof smaller bags may allow a greatermesh bag density to be used. No effect(P>.05) of mesh bag density wasobserved. Therefore, up to 50 in situbags can be placed in one mesh bag andup to 300 in situ bags (5 × 10 cm) can beincubated in a large, fistulated bovine.Similarly, no effect (P>.05) was foundfor position of bags within the bulkrefluxing apparatus. Bags may be allot-ted randomly to any dish in the bulkreflux rack without affecting NDFNcontent. No differences (P>.05) betweenreflux times or extent of post-neutraldetergent extraction rinsing wereobserved. These results imply refluxtime and extent of rinsing are not criti-cal to the method.

Previous estimates of in situ NDFNUIP assume NDFN is 100% digestiblein the rumen. However, this assumptionis inconsistent with cell wall digestionmodels, which assume ruminallyundegradable fiber exists. It is impor-tant to have an accurate estimate of k

d

for a UIP fraction. The purpose ofExperiment 4 was to describe the effect


age type at a location, corrected NDFNUIP values can be estimated from un-corrected values using the predictionequation.

In summary, the results of Experi-ments 1, 2, 3 and 4 imply all testedmodifications can be implemented intoan improved method. Such a methodwill save time and money relative to thestandard in situ procedure and will pro-vide more accurate estimates of forageprotein degradability. Information ob-tained by this method will contribute tomore accurate use of the 1996 NRCBeef Cattle software.

1Ryan Mass and Greg Lardy, researchtechnicians; Rick Grant, Associate Professor; andTerry Klopfenstein, Professor, Animal Science,Lincoln.

Table 1. Regression equations for correcting the rate of in situ neutral detergent fiber nitrogen(NDFN) digestion for an undegradable fraction.

Sample Set n Equation r2

Native Winter Range 24 .468 + 1.174X + .023X2 .952

Cornstalks 24 .584 + .956X + .035X2 .946

Vegetative Cool-Season 36 .176 + 1.221X + .051X2 .804Grasses

Combination of all sets 84 .400 + 1.227X + .028X2 .854

X = uncorrected rate of digestion calculated from 2 and 12-hour in situ NDFN content

of correcting the NDFN kd for an

undegraded nitrogen fraction. Theamount remaining after 96 hours wasassumed to be undegradable in therumen.

Regression equations describing theeffect of correcting for an undegradableUIP fraction are shown in Table 1. The

equations explain a high proportion ofthe variation in NDFN k

d (i.e. r2 >.80).

Equations for cornstalks and nativewinter range were not statisticallydifferent.These results imply a closerelationship exists between the twomethods of calculating k

d. When equa-

tions are developed for a particular for-

Tenderness and Retail Stability ofHydrodyne-Treated Beef

Bernadette O’RourkeChris CalkinsRose Rosario

Morse SolomonJohn Long1

The potential exists to use anexplosively-generated shock wavein water to tenderize beef. No det-rimental changes to product dis-play or shelf stability characteristicsare created by the Hydrodyne pro-cess.

Summary

Detonating a small explosive withina water-filled, stainless steel tank, cre-ates a shock wave which penetratesvacuum-packaged meat. The acousti-cal match between water and meatcaused an immediate and significant(P<.05) reduction in shear force. After

an additional 10 days of aging, notenderness differences (P>.05) weredetected. Hydrodyne created no differ-ences in pH, sarcomere length, purge,oxidative rancidity, bacterial counts(anaerobic or aerobic) or panel colorratings for either cut. Treated sampleshad higher Hunter L* values. TheHydrodyne process can tenderizeunaged meat with no detriment to prod-uct display or shelf stability character-istics.

Introduction

Tenderness, the primary factor de-termining palatability and overall con-sumer satisfaction of meat, isinconsistent, creating significant con-sumer concern. Therefore, technolo-gies to enhance tenderness can improveboth product quality and customer sat-isfaction.

In the Hydrodyne process, vacuum-packaged meat is placed within a stain-

less steel hemispherical tank and im-mersed in water. Detonation of a smallamount of explosive within the watergenerates a shock wave which pen-etrates the meat, strikes the sides of thetank and reflects back through the meat.The entire process takes place in anencapsulated steel tank to contain theexplosion and the resulting water splash.

The shock wave generates up to10,000 psi of force which appears tocause immediate and significant reduc-tion in shear force. One reason for thetechnique’s effectiveness is the acous-tical match between the liquid medium(water) and the meat, which is 70-75%water. Connective tissues and bone seemless affected by the process.

Severe disruption of the muscle ul-trastructure might be expected to con-tribute to enhanced proteolysis andoxidation, creating enhanced tender-ness but reduced retail storage life. Thisresearch was conducted to determinethe effect of the Hydrodyne process on


tenderness, oxidative rancidity, colorand microbial growth during storageand retail display of beef.

Procedure

Sixteen beef strip loins and 16 rounds(8 Control [C] and 8 Hydrodyne [H]each) were selected, vacuum-packagedand shipped to the Hydrodyne facility(Buena Vista, VA) for testing. Fivedays postmortem, the meat was placedwithin the water-filled hemisphericaltank. The explosive mixture (ammo-nium nitrate and nitromethane) waspositioned in the water 18 in. from thebottom of the tank and detonated. Theresulting shock force was estimated tobe 4,000 psi.

All meat was then transported to theBeltsville Agricultural Research Cen-ter in Beltsville, Maryland and repre-sentative samples were removed,repackaged and shipped on ice to theUniversity of Nebraska, Lincoln, Ne-braska. Samples were taken at threedifferent periods: after shipping, afterstorage and after retail display. Follow-ing shipping, strip loins were sampled(day 7), repackaged in vacuum andstored an additional 10 days at 40oFbefore sampling during the beginningand end of a retail display period. Toprounds were sampled (day 10), pack-aged and stored an additional 7 daysbefore sampling as previously described.Analysis of pH, purge, thiobarbituricacid-reactive substances (TBARS),aerobic plate count and anaerobic platecount were conducted after a shippingperiod, at the beginning and at the endof a retail display period (day 7, 17, 21for strip loins and day 10, 17, 21 for toprounds). Panel discoloration scores (lean

color, surface uniformity and surfacediscoloration) and Hunter colorimeterlab values were obtained for both cutseach day of the retail display period.Warner-Bratzler shear force (day 7, 17)and sarcomere length (day 7) were col-lected only on strip loins.

For retail display, samples were ran-domly positioned in the retail case andrepositioned each day. Samples weremaintained at 40oF with light rangingfrom 20-50 foot candles. Strip loin steakswere broiled to an internal temperatureof 158oF and as many .5- in diametercores were obtained as possible (8-10cores). The cores were sheared parallelto the long axis of the muscle fiber.Cooking loss and cooking time werealso recorded.

Results

Hydrodyne treatment of the striploins caused a significant decline inshear force (Table 1) measured twodays after treatment (7 days postmor-tem). This was an immediate and mean-ingful decline. An extended aging period(17 days postmortem), removed the ten-derness benefits of the process (no dif-ference in shear force). It is interestingto note that shear force was generallyacceptable in all samples (<7.72 lbs),yet Hydrodyne still proved beneficial.Previous research on the process indi-cated over-tenderization does not seemto occur and that tough longissimusmuscles seem to benefit more fromHydrodyne treatment than tender long-issimus muscles. These data suggestaging may allow untreated meat to reacha similar level of tenderness. A study tocompare aging time and Hydrodynetreatment is needed to determine the

extent to which tenderness benefits ofaging supersede the benefits from theHydrodyne process. Insufficient sam-ples were collected from the top roundto permit an assessment of shear forcein these muscles.

No differences among the treatmentswere consistently found in muscle pH,sarcomere length or purge for eithercut. All samples exhibited a high amountof purge, probably due to temperaturefluctuations during the shipping period.This may have masked any treatmentdifferences.

It was anticipated that Hydrodynetreatment might enhance oxidative ran-cidity before retail storage. All TBARS(a measure of rancidity) were below0.4. This is well below 1.0, the point atwhich rancidity is usually detected. Inthis study, extended retail display afteran extended storage period increasedthe amount of thiobarbituric acid-reac-tive substances (Table 1). However, nodifferences among treatments were re-vealed for either cut (.34 [H] vs .36 [C]in strip loins, d7 and .26 [H] vs .25 [C]in top rounds, d10). There was a trendfor Hydrodyne-treated strip loins to havea lower TBARS readings after extendedretail display, but this difference wasnot consistent enough to be significant(.83 [H] vs 1.28 [C] for the strip loins(P>.05) and 1.48 [H] vs. 1.37 [C] for thetop rounds (P>.05). Thus, it appears theHydrodyne process does not compro-mise rancidity, which impacts flavorstability.

It should be noted that while micro-bial numbers were extremely low (<500cfu/square in), in all cases, theHydrodyne-treated rounds possessedslightly, but significantly, higher

Table 1. Characteristics of Hydrodyne-treated beef strip loins and top rounds.

Strip loins - time post-mortem Top Rounds - time post-mortem

d7 d17 d21 d10 d17 d21

Trait Ca Ha C H C H C H C H C H

Shear force, lb 7.12c 6.20d 5.60d 5.84d — — — — — — — —TBARSb .36c .34c .20c .21c 1.28d .83d .25c .26c .18c .32c 1.37d 1.48d

Aerobic plate count, cfu/in2 73.2c 38.0c 52.4c 53.4c 453.0d 124.9c 61.9c 30.8c 50.0c 16.9c 477.1c 71.8c

Anaerobic plate count, cfu/in2 55.7c 63.3c 14.8d 5.3d 12.2d 5.8d 4.1c 27.6d 8.5c 4.2c 1.4c 4.4c

aC=Control (untreated); H=Hydrodyne - Treated.bTBARS=Thiobarbituric acid - reactive substances, a measure of rancidity.c,dMeans in the same row bearing different superscripts are different (P<.05).



numbers of anaerobic microbes afterstorage and shipping, which did notcarry through retail display. Previousresearch suggested a slight but signifi-cant reduction in microbial numberswhen the Hydrodyne process was ap-plied. A similar trend noted for aerobicplate count in the strip loin and roundsamples was attributable to a singlesample of each muscle with a muchhigher count than all other samples,regardless of treatment (Table 1). Nocredible reason could be found for ex-cluding the data points. As expected,the number of anaerobic micro-organ-isms declined during retail display. Nodifferences were detected at the initia-tion or the conclusion of the retail dis-play period.

Lean color, surface uniformity andsurface discoloration panel scoresrevealed no differences among treat-ments in either cut. Hunter color L*values were higher in the Hydrodynestrip loins and top rounds, indicatingHydrodyne was slightly lighter(P<.05) than the control (43.84 [H]vs. 41.70 [C] for the strip loins and45.34 [H] vs. 44.53 [C] for the toprounds). These data indicate theHydrodyne process can tenderizeunaged meat with no detriment toproduct display or shelf stability char-acteristics. Further study on the processis needed to clarify the Hydrodyne/aging relationship and to refine thetechnique prior to commercialization.

1Bernadette O’Rourke, graduate student; ChrisCalkins, professor; Rose Rosario, researchtechnician, Animal Science, Lincoln. MorseSolomon, researcher, USDA, ARS, Meat ScienceLab, Beltsville, MD and John Long, Hydrodyne,Inc., San Juan, PR.

Dietary Calcium andPhosphorous: Relationship toBeef Tenderness and Carcass

Maturity

Dana HansonChris Calkins

Galen EricksonMark Klemesrud

Todd MiltonTerry Klopfenstein1

Dietary levels of calcium andphosphorous for finishing cattlehave no effect on overall maturityscores and tenderness of beef.

Summary

The effect of dietary mineral statusas related to carcass maturity or meattenderness was studied. Finishing year-ling steers were individually fed vary-ing levels of calcium and phosphorous.Neither mineral was significantly re-lated to overall carcass maturity scoresor meat tenderness. When fed at thelevels in this trial, it appears there areno adverse effects of dietary calciumand phosphorous on carcass or meatcharacteristics.

Introduction

Beef carcass maturity is determinedby visually assessing lean color and thedegree of ossification (conversion ofcartilage to bone) in the skeleton.Younger animals (about 9-30 months

of age) usually possess characteristicsof “A” maturity. Maturity classifica-tion is important, as advancing matu-rity is often associated with a decline inmeat tenderness. Recent changes in theUSDA quality grades for beef impose astrict penalty for carcasses which pos-sess small or slight amounts of mar-bling and “B” maturity (the nextclassification after “A” in the qualitygrading system). Carcasses, whichwould formerly have qualified forChoice and Select grades now qualifyonly for Standard grade. Accordingly,it is important to determine factors whichinfluence physiological maturity andossification. Current speculation sug-gests mineral status may play a role inthe ossification rate, meaning youngeranimals with improper mineral statusmight be classified as older than “A”maturity, with a subsequent loss of value.This project was conducted to assessthe relative significance of dietary Caand P on maturity scores and beef ten-derness.

Procedure

Sixty yearling crossbred steers wereindividually fed once daily from Sep-tember 4 to December 18, 1996 (105 d).Steers were randomly assigned one of10 treatments, consisting of two levelsof calcium (Ca), either 0.35 or 0.70 % ofthe dietary DM, with limestone as the


100

80

60

40

20

0

Lean

Mat

urity

, % o

f A M

atur

ity

.14 .19 .24 .29 .34

Dietary Phosphorus, %

.35 Dietary Calcium % .70 Dietary Calcium, %

Figure 1. Dietary mineral level and beef lean maturity.


80

60

40

20

0

Ove

rall

Mat

urity

, % o

f A M

atur

ity

.14 .19 .24 .29 .34


.35 Dietary Calcium, % .70 Dietary Calcium, %

Figure 2. Dietary mineral level and beef overall maturity.


80

60

40

20

0

Ske

leta

l Mat

urity

, % o

f A M

atur

ity

.14 .19 .24 .29 .34


.35 Dietary Calcium, %, P<.05 .70 Dietary Calcium, %

Figure 3. Dietary mineral level and beef skeletal maturity.

14

12

10

8

6

4

2

0

She

ar F

orce

Val

ues,

lbs

Figure 4. Dietary mineral level and beef tenderness.

.14 .19 .24 .29 .34


.35 Dietary Calcium, %, P<.05 .70 Dietary Calcium, %


source of supplemental Ca. Within eachCa level, there were five levels of phos-phorous (P): 0.14, 0.19, 0.24, 0.29 or0.34% of dietary DM. Supplemental Pwas provided by mono-sodium phos-phate (NaP). Diets during this trial wereformulated for 12% protein. Cattle werealso implanted with Revalor-S® at thestart of the trial.

Carcass data (lean maturity, skeletalmaturity, overall maturity and marblingscore) were assessed by a Federal USDAMeat Grader and recorded at the meatplant. Wholesale rib sections (IMPS122A) were shipped to the Universityof Nebraska, aged for 7 days, then fro-zen. A one-inch thick steak was re-moved for tenderness assessment.Thawed steaks were cooked on aFarberware Open Hearth broiler to aninternal temperature of 158oF, cooledto about 70oF, and 8-10 cores (1/2 inchin diameter) were removed parallel tofiber direction. The cores were thensheared using a Warner-Bratzler shearattachment to an Instron Universal Test-ing Machine.

The analysis of variance includedCa and P as main effects. Significant

(P< .05) interactions were separatedusing contrasts to test for linearity.

Results

Dietary levels of Ca and P had noeffect on either lean maturity or overallmaturity scores (Figures 1 and 2). Thiswas to be expected, as there is littleinformation that suggests Ca or P wouldaffect meat color. Given the slight ef-fect on skeletal maturity and no effecton lean color, it was expected therewould be no effect on overall maturitybecause of dietary Ca and P levels.

Figure 3 graphically depicts the rela-tionship of dietary mineral level andbeef skeletal maturity. At 0.35% di-etary Ca, skeletal maturity score de-creased in a linear relationship (P < .05)with an increase in dietary phospho-rous. Higher levels of dietary P mightbe expected to cause an increase inossification, as Ca and P act synergisti-cally to form bone. However, the mag-nitude of the skeletal maturity differencewas slight (A 70 to A 48). While asignificant relationship did exist, theeffect on skeletal maturity was mini-

mal. Changing diet formulations to gar-ner this response may not be merited.The relationship was not significant atthe 0.70% Ca level. In related work,Erickson et al. (1998 Nebraska BeefCattle Report, pp. 78) found no differ-ence in animal gain or bone strengthfrom the cattle used in this trial.

No significant correlations werefound linking tenderness to skeletal oroverall maturity. The range in cattleage in the study may have been insuffi-cient to detect the overall relationship.Lean maturity scores were related (r=.29, P<.05) to shear force.

No significant relationships werefound among mineral levels and meattenderness (Figure 4). These data indi-cate Ca and P, at the levels used in thisstudy, are not responsible for maturityor tenderness changes in beef.

1Dana Hanson and Galen Erickson, graduatestudents. Chris Calkins and Terry Klopfenstein,Professors, Animal Science, Lincoln. Todd Milton,Associate Professor, Animal Science, Lincoln. MarkKlemesrud, research technician.

Career

Your undergraduate degreewith an Animal Sciencemajor prepares you for anumber of careers in thelivestock and meat industriesas well as professional studyin veterinary medicine,medicine, law or teaching.

Universityof

Nebraska-Lincoln

You select course workranging from animalmanagement to in-depthscientific studies to buildyour own specializedprogram.

Animal ScienceCollege of Agricultural Sciences and Natural Resources

Resources

You also have opportunitiesfor hands on experiencethrough internships and classtours of agribusinesses andproduction units across thecountry. And you study instate-of-the-art laboratoriesand classrooms.

Activities

As an Animal Sciencemajor you may beparticularly interested inBlock & Bridle to buildleadership, communicationand organizational skillswhile you meet new friendswith similar interests.

Courses

N E B R A S K Aextensionpublications.unl.edu/assets/pdf/mp69.pdf · 2015-09-10 · Weaning date...

Documents

Transcript of N E B R A S K Aextensionpublications.unl.edu/assets/pdf/mp69.pdf · 2015-09-10 · Weaning date...