F o r a g e U p d a t e 2 0 1 0 

Corn Silage Hybrid Selection

Bill Mahanna, Ph.D.

Nutritional Sciences Manager

Pioneer HiBred International

 

1

Decisions made in the fall on hybrids to plant next spring will impact you for the entire year

Bill Mahanna, Ph.D., Dipl ACANNutritional Sciences ManagerPioneer, A DuPont Businessbill.mahanna@pioneer.com

515.229.3409

Various University and Seed Company Plots Prove Genetic Differences Certainly Exist

But you have to interpret the plot data using valid statistics

When hybrids are statistically different, then apply biological

relevancy to thedifferences. For example,

comparing the nutritional value of 1% unit difference in NDFDof 1% unit difference in NDFD

(~50-60% digestible) versus 1% point differences in starch content (>90% digestible).

Measured Silage Yield DifferenceNumber of

Environments/Plots 2.0 T/A 1.0 T/A 0.5 T/A

1 60% 52% 51%

10 90% 75% 65%

30 95% 90% 75%

200 98% 95% 93%

After hybrids have been screened for agronomic and technology traits, theUW Consortium recommends these

corn silage selection priorities:

Source: http://corn.agronomy.wisc.edu/AAdvice/1997/A015.html

1st Grain Yield2nd Whole Plant DM Yield3rd Standability (in case want to take for HMC or even dry corn)

4th Relative Maturity5th Quality (e.g. fiber digestibility)

2

….….Because University data shows there Because University data shows there are are minimal genetic differencesminimal genetic differences (4(4--5% units) 5% units)

between conventional hybrids for fiber digestibility between conventional hybrids for fiber digestibility and small differences in starch content quickly and small differences in starch content quickly

overwhelm the increased energy from NDFD overwhelm the increased energy from NDFD

growing conditions, Heritability of NDFD is high but the growing conditions,

harvest timing,

chop height,

fermentation quality

feed-out management

Heritability of NDFD is high but the range (variation) among commercial,

high yielding germplasm is low.…..and remember, it doesn’t help to

apply selection pressure to a trait with minimal genetic variation

growing conditions, growing conditions,

harvest timing,

chop height,

fermentation quality

feed-out management

70 26Nitrogen

70+ 27Weather

2

1

bu/acre %

ValueFactorRank

Factors Impacting Corn Factors Impacting Corn GrainGrain YieldYieldDr. Fred Below – University of Illinois, Urbana-Champaign

The huge impact of growing environment explains why hybrids can perform so differently from location-to-location and from year-to-year. This applies to corn grain and corn silage.

10 4Growth Regulators

15 6Tillage

20 8Plant Population

25 10Previous Crop

50 19Hybrid

7

6

5

4

3

260bu 100%Total =Assumes key prerequisites of weed

control and soil fertility are met Source: http://magissues.farmprogress.com/OFM/OF02Feb09/ofm016.pdfhttp://www.cropsci.illinois.edu/faculty/below/

Lets now look at the Lets now look at the impact of growing impact of growing environment on silage environment on silage hybrid data….hybrid data….

Which silage hybrid would you choose?Which silage hybrid would you choose?

A B C D E F G H I J K L M N

Source: Dann Bolinger, M.S. – Pioneer Dairy Specialist, Michigan

3

SurpriseSurprise….they are all the ….they are all the samesame hybrid hybrid (34A89) but grown in (34A89) but grown in differentdifferent locations in locations in Michigan in 2009Michigan in 2009

Source: Dann Bolinger, M.S. – Pioneer Dairy Specialist, Michigan

Hybrids will respond Hybrids will respond differentlydifferently for for tonnage yield tonnage yield in in differentdifferent growing environmentsgrowing environments

Alto

Saranac

Fowler

Elsie

Clare

Caseville

2009 plots with common hybrid entries2009 plots with common hybrid entries

2nd

Last

1st

Last

Which is why 20+ comparisonsacross multiple growing yearsis essential to compare hybrids

Last 3rd

Source: Dann Bolinger, M.S. – Pioneer Dairy Specialist, Michigan

Starch InfluencersStarch Influencers• Yield is roughly 50% grain

• % Starch is ratio of grain to fodder– Early vegetative growth w/ mid to late season grain fill

• Maturity @ harvest• Maturity @ harvest– Prior to black layer, starch is still being produced

– Hybrids within a plot should be reasonably close in maturity • look at harvest moisture as an indicator

Hybrids will respond Hybrids will respond differentlydifferently for for starch yield starch yield in in differentdifferent growing environmentsgrowing environments

Alto

Saranac

Fowler

Elsie

Clare

Caseville

2009 plots with common hybrid entries2009 plots with common hybrid entries

Last

1st

2nd

4th

% S

tarc

h

Source: Dann Bolinger, M.S. – Pioneer Dairy Specialist, Michigan

V6• Begins rapid growth stages

• Begin to determineyield potential

• Poor time to stress crop due to lack of water

VT (Tassel)

• Water & fertilityrequirements aresignificant

• Next stage is“Reproductive”

• Ear size/length and number of kernels per row isto lack of water

• Ear Girth and number of kernels around the ear is determined

kernels per row is determined

16 around 20 around

Note the date when your corn silked:Tasseling / silking corn plants have ~900 GDUs to reach silage maturity

Count ahead six weeks and that’s about when you should get serious about checking maturity status.

You might have read that corn will reach “silage maturity” 35-45 days after silking, but usually that’s 30% Stage of

MaturityApprox days to g y

DM and because of avoiding effluent and increased starch deposition, it is advisable to wait until the corn is a few percentage points dryer than 30%.

Most of the difference between hybrids of different relative maturities is between emergence and silking, not from silking to the 32-35% dry matter that’s ideal for corn silage.

Maturity ½ Milkline

Silking 35-45

Blister 25-35

Late Milk 15-25

Early Dent 5-15

Source: Pioneer Research and Ev Thomas, August 2007 Miner Farm Report

It is not unusual for silage to dry down .5-1.0 points of moisture per day, depending upon drying conditions. It is also not

unusual for corn silage to lay down .5-1.0 points of starch per day until kernel reaches physiological maturity at blacklayer

(starch deposition significantly contributes to reducing moisture in whole plant samples as the plant matures)

4

Starch

½ ML

¾ ML

Harvesting too premature will cost you starch yields Germ

96.1 95.2 94.1

60

80

100

120

DM

or

of N

utr

ient

Composition and Digestion Changes with Silage DM

Starch Digestibility (Processed)

With the cost of grain today, increased starch content of silage compensates for relatively small decreases in NDF digestibility (and dilutes NDF)

Source: Dr. Fred Owens, Pioneer Senior Research Scientist. Journal of Animal Science and Journal of Dairy Science literature review summary

27.530.9 33.4

18.0 16.7 15.3

41.2 39.3 38.4

47.2 45.3 44.3

0

20

40

30 32 34 36 38 40

Silage Dry Matter, %

Val

ue,

% o

f D NDF Digestibility

NDF Content

Starch Content

Sugar + Organic acid Content

When selecting a silage hybrid, don’t get When selecting a silage hybrid, don’t get hung up on hung up on marketing hype or labels such as:marketing hype or labels such as:

silagesilage--specific…….specific…….

dualdual--purpose…..purpose…..

grain hybrids….grain hybrids….Rather, rely on multi-year data for important traits such as yield and starch content, just like you rely on bull proof date, not the name of the bulls you are using in your herd….

NDFD vs Grain yield (Wisconsin Silage Tests)

68

70

72

74

ity,

%

<90 d91-100 d101-105 d106+ dNDF

R2 = 0.0033

R2 = 0.027

R2 = 0.0877R2 = 0.0393

58

60

62

64

66

68

75 100 125 150 175 200Grain yield, bushel/acre

ND

F D

iges

tibili

NDF yield vs Grain yield (Wisconsin Silage Tests)

R2 = 0.2025

R2 = 0.08744.5

5.0

acre

<90 d

91-100 d

101-105 d

106+ d

R2 = 0.0379R2 = 0.0183

2.5

3.0

3.5

4.0

75 100 125 150 175 200Grain yield, bushel/acre

ND

F y

ield

, to

n/a

• To be a good silage hybrid, it must start out as a good grain hybrid because you can not overcome lack of starch (>90% digestible) with small increases in fiber digestibility (60-70% digestible)

• BUT…not every grain hybrid makes a good silage hybrid because they may be too short and not deliver the desired stover yields

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NDFD InfluencersNDFD Influencers• Greatest during vegetative growth (pre-tassel)

• Early moisture stress = improved NDFD– Moisture availability

• More water typically lower NDFDyp y

• Less water typically higher NDFD

• Heat Units– More heat, less NDFD

– Less heat, more NDFD

• The weather before and after silking (R1) appears to affect final corn silage nutritive value– Before silking, weather affects

corn plant height (and yield) and p g ( y )fiber quality

• Dry conditions => higher NDFD

• Wet conditions => lower NDFD – but not as much if heat units are

lagging behind normal

– After silking weather affects corn grain yield, NDS:NDF ratios and total DM digestibility

Source: Mertens, 2002 Cornell Nutrition Conference

R1 R1 -- SilkingSilking

Growing environment during stalk development (June 1 thru July 15)

Hybrids will respond Hybrids will respond differentlydifferently for for NDFD NDFD in in differentdifferent growing environmentsgrowing environments

Wet with moderate heatWet with moderate heatwet with wet with high heathigh heat

dry with dry with mod mod heatheat

dry with low heatdry with low heat

Plots grouped by 2009 growing environment during stalk development - June 1 to July 15

- Moisture and heat effected NDFD of all hybrids, but moisture had a greater influence.-Some hybrids were more susceptible to environmental influences (blue hybrid)

Source: Dann Bolinger, M.S. – Pioneer Dairy Specialist, Michigan

Impact of Growing Environment on NDFD Shown by the Drought-Stress Effect of the Same Hybrids Grown in 2006 (wet year)2006 (wet year) vs. 2007 (drought year)2007 (drought year)Impact of Growing Environment on NDFD Shown by the Drought-Stress Effect of the Same Hybrids Grown in 2006 (wet year)2006 (wet year) vs. 2007 (drought year)2007 (drought year)

Source: Dann Bolinger, Pioneer Dairy Specialist - Michigan

What is one point of forage NDFD worth?

Meta-analysis of published studies with a variety of

forages and a large range of NDFD (24-87%) showed a .37lb increase in DMI and

55lb i i ilk

Oba and Allen, MSU

Source:  Jung, H.G., M, Raeth‐Knight and J.G. Linn.  2004.  Forage fiber digestibility: measurement, variability and impact.  Proceedings Minnesota Nutrition Conference

a .55lb increase in milk

For CS (at least 40% of the

diet), the results showed a .25lb increase in DMI and

a .3lb increase in milk

Source: Mertens, D.R. and P. Berzaghi. 2009b. Silage quality and dairy production. Proceedings 15th International Silage Conference. Monona Center, Madison, WI. July 27-29, 2009. p. 101-114.

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High-chopping corn silage allows producers the option of “dialing in” desired fiber digestibility

for transition & high string rations

Review of 11 Scientific and Popular Press

articles on high-chopping by Wu and Roth at

Penn StatePenn State

Source: http://www.das.psu.edu/user/publications/pdf/das03-72.pdf

3.4% unit increase

Concentrated Concentrated more starchmore starch

You Do Give Up Some Yield When High-Chopping

For each 4 inches (10 cm) of increased cutting height– expect yields to be reduced by 1 as fed silage ton (909kg, 30%DM) per acre

– But what you leave in the field are stalks, not high-starch corn silage

Chop Height Influence on NDFD

40 00

50.00

60.00

cu

ba

tio

n

9” cut34.2%

18” cut39.7%

27” cut51.7%16% increase

Pioneer Chopping Height Field Trial Year 1 (New York, 2000)

There appears to be a significant Genetic x Growing Season Interaction

0.00

10.00

20.00

30.00

40.00

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

ND

FD

- 2

4 h

ou

r in

34B23

Cutting Height Influence on NDFD

50.00

60.00

cu

ba

tio

n

9” cut 29 9%

18” cut 31.7%

27” cut 50.1%5% increase

67% increase

There appears to be a significant Genetic x Growing Season Interaction

Pioneer Chopping Height Field Trial Year 2 (New York, 2001)

This season only a 5% increase

0.00

10.00

20.00

30.00

40.00

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

ND

FD

- 2

4 h

ou

r in

c 29.9%

34B23

• Hand-chop representative plants and analyze NDFD before chopping

• Then alter chop height based d i d NDFD d NDFD

You Can Vary Silage Chop Height Depending upon You Can Vary Silage Chop Height Depending upon the Silage Growing Season the Silage Growing Season and the Quality of the and the Quality of the Haylage Already in Storage…..Haylage Already in Storage…..

on desired NDFD and NDFD of other forages in storage (e.g. hay haylage)

• The growing season influence on NDFD requires pre-testing the crop to determine the exact NDFD impact from high chopping

7

Field example of monitoring the growing season Field example of monitoring the growing season effect and influence of higheffect and influence of high--choppingchopping

34M93 10”

34M93

22”

33P62

10”

33P62

22”

Average Values

% Moisture 70.6 69.6 70.7 70.9 65-68

% starch 17.0 23.6 14.9 17.5 30-35

5 representative plants hand-cut by sales rep Tom Hemesath on 8-15-05. Data from Pioneer lab reported back 8-17-05.

% Sugar 6.6 4.5 7.3 7.1 6-8

% Str + Su 23.6 28.1 22.2 24.6 ??

% NDF 55.4 51.5 56.6 53.7 45-50

% NDFD(24 hrs)

39.2 44.1 42.2 43.7 45

% CP 6.3 6.6 7.4 8.0 7-8

% ash 4.6 3.8 5.3 4.9 4-5

Note the hybrid (and/or sampling) effect in that 33P62 did not show a very big improvement in NDFD with high chopping

Inoculation: Inoculation: another approach to improving NDFD….another approach to improving NDFD….

PLUS– Improves consistency

– Reduces shrink (DM loss)

4th generation product to vastly improve NDFD

Pioneer has received official Canadian government Pioneer has received official Canadian government approval to make the following claims for 11CFT:approval to make the following claims for 11CFT:

1 I d d tt i t k1. Improved dry matter intake 2. Improved NDF digestibility 3. Improved gain/tonne of silage fed 4. Improved feed efficiency 5. Reduced heating at feeding 6. Reduced dry matter loss at feeding

Registration received January 5, 2007

CFT breaks this ester bond with an enzyme produced in the bunker by our L. buchneri strain, allowing rumen bacteria to digest the cell wall much faster because it is separated from the lignin.

“Fiber and Lignin”are similar to

“Concrete and Rebar”

After CFT

Before CFT

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1. Assume slightly higher intakes (hence more starch intake)

2. Be sure ration has adequate effective fiber (peNDF scratch)(peNDF, scratch)

3. Increase the energy density of CFT-silage by assuming a 4-percentage point increase in NDFD

These are all still valid, but #3 did not provide adequate direction for consulting nutritionists

If nutritionists use If nutritionists use Net Energy (NENet Energy (NE--L), L), changing changing NDFD NDFD 44--points results points results in in very minor changesvery minor changes in NEin NE--L estimates. L estimates. We do not think NEWe do not think NE--L will be L will be

sensitive sensitive enough enough to to the the digestion rate changes digestion rate changes we see with CFT.we see with CFT.

4 points of NDFD only increased NE-L .01 Mcals

CNCPS V6.1

CPM

Portion of NDF that

CFT frees up

FastKd’s

SlowKd’s

We use to think the B3

pool was the only onechanged in CFT-silage

Independent Research Substantiating Pioneer’s CFT Data

Some Some nutritionists nutritionists use the use the increase in NDFD to adjustincrease in NDFD to adjustNDF (BNDF (B33) digestion rates ) digestion rates (Kd’s) (Kd’s) with a Cornell spreadsheetwith a Cornell spreadsheet

Dr. Mike VanAmburgh’s NDFD Kd calculator available from Cornell University or Pioneer

CNCPS V6.1

CPM

In this corn silage, a 4In this corn silage, a 4--point point increase in increase in NDFD NDFD translates translates to a 15to a 15% higher % higher KdKd

Lets see how this approach works in a real ration

9

Using the example lactating ration (and feed library corn silage) that comes loaded in CNCPS (Feed library corn silage parameters are 35%DM, 35.5% STR, 41% NDF, 2.87% lignin, 3.4%/hr B3, 30%/hr B1, 30%/hr B2)

Milk predicted from the metabolizable

energy (ME) or metabolizable protein

(MP) in the ration

Same ration with CS modified to account for CFT by changing B3 rate using VanAmburgh calculator (4 pts NDFD) from 3.4% to 3.9%/hr

CFT increased the predictedME milk by .87 lbs

and MP milk by 1.1 lbs

• To produce the same ME and MP milk as the non-CFT silage ration, you can remove .37 lbs of corn meal whenof corn meal when feeding CFT-silage

• With corn @ $3.50/bu corn this resulted in a savings of 2.3 cents/c/d

Using CPM ration software to compare control vs. CFT in 7 side-by-side field trials with vacuum packed silage for which gas-production data was generated….

BUT NOW

Kd’s on all the pools (B1, B2 and B3) were modified based on the averages of the gas g gdata shown below.

0.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

16.0

Fast Pool Kd %/h Slow Pool Kd %/h Fast Pool time to max, hr

Slow Pool time to max, hr

% K

d/H

r o

r H

ou

rs t

o M

ax11CFT

Competition

Faster is better for high producing cows with rapid rumen turnover

rates

Less time to reach maximum digestion rates is preferred for high producing cows

with rapid rumen turnover ratesC

FT

CFT

CFT

control

control

Fast PoolKd, %/hr

Slow PoolKd, %/hr

Fast Pooltime to Max, hr

Slow Pooltime to Max, hr

Kd rates based on average gas data for NDF(B3) by 35%

B1 by 50%

and B2 by 30%

CFT silage now predicted toCFT-silage now predicted to increase ME by 1 lb (.45 kg)

and MP by 4.3 lb (1.9 kg)compared to control CS

Biological reality Biological reality is probably somewhere in the is probably somewhere in the middle!middle!

Compared to ME milk .87 lb (.39 kg)and MP by 1.1 lb (.5 kg) when

adjusting B3 rates aloneKept grain at 5.2 lbs versus 5.57 lbs in the

original ration

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Protein savings, from more rumen microbial growth on CFT-silage, contributes more to decreasing ration costs than the

effect of reducing corn meal in the ration.

What about protein?

Fate of Proteins in Ruminants

Back to the Base Ration using Feeds From the CNCPS Feed LibraryBack to the Base Ration using Feeds From the CNCPS Feed Library(35%DM, 35.5% STR, 41% NDF, 2.87% lignin, 3.4%/hr B3, 30%/hr B1, 30%/hr B2)

Milk predicted from the metabolizable

energy (ME) or metabolizable protein

(MP) in the ration

Note the production of microbial protein from

this “base” ration is 1326 grams

Notice relatively low CP level of this ration predicted to generate 43.87 kg of MP milk….this is consistent with

where Cornell is recommending nutritionists alance

protein…remember, this is the example ration that comes loaded

with the CNCPS program

Now with changing the digestion rates of B1,

B2 and B3, the production of

microbial protein was increased by 93 grams over the basal diet and 76 grams over the CFT

ration with only B3 rates increased (from

3.4 to 3.9%/hour)

All ration ingredientskept constant

In this ration, soybean meal was reduced from 2.33 lbs to 1.70 lbs (did not change anything else, so DM intake will be lowered accordingly). Now the predicted ME and MP milk is similar to what was predicted with the original base ration (90.12 and 96.51). Reducing soybean meal by .63 lbs @$350/ton = 11cents/c/d savings. Note this reduced the CP level to 15.9%.

Note that even when removing

.63 lbs of soybean meal, the production

of microbial protein is still 86

grams better than the original

base ration

Key points are that CFT appears to:Key points are that CFT appears to:1. Increase the rate of B3 (“slow pool”) digestion by upwards of 35%; causing B3 nutrients

A 4% point increase in 48-hour NDFD (over baseline estimates) is a reasonable starting point to factor in the effect of CFT. Changes in digestion rates (Kd) of the B3 pool (available NDF) resulting from the improvement in NDFD can be made in

formulation models, such as CPM or CNCPS, by employing the VanAmburgh Rate Calculator (VARC) available from Cornell professor, Dr. VanAmburgh (mev1@cornell.edu) or from Pioneer. However, field experience suggests that increasing B3 rates

by 15-20 %, (which VARC predicts from a 4-point increase in NDFD), will not fully account for the effect of CFT and adjustments will likely be required in the rates of B1 (starch) and B2 (soluble fiber) pools to prevent over-feeding of concentrates

(e.g. hemicellulose) to digest at rates more commonly observed among “fast pool” (B2) nutrients (e.g. soluble fiber)

2. Reduce the time required to achieve maximum B3 (slow pool) digestion rates 3. Increase the digestion rates of both the B1 and B2 pools by upwards of 30-50%. 4. Feeding CFT silage typically allows for reduction in “fast pool” nutrients (e.g. starch).

In practice, this means reducing concentrate (grain) in the TMR to offset increased availability of hemicellulose and the shifting of “slow pool” nutrients into the “fast pool”.

5. Field experience with herds who experienced milkfat depression problems when starting to feed CFT-silage, were typically borderline for effective fiber and/or acidosis issues and quickly resolved the problem (and lowered feed costs) by reducing grain (especially HM corn), increasing corn silage inclusion rates (and effective fiber) and/or adding co-products such as soyhulls (additional source of soluble fiber).

6. CFT silage-based rations may require attention to protein formulation; allowing for the reduction of rumen degradable and/or undegradable protein due to increased bacterial protein production and MP milk predicted when CFT-silage digestion rates are modeled in CPM or CNCPS.

One One Topic Related to Feeding Topic Related to Feeding CSCSChanging starch digestibility overChanging starch digestibility over

time in time in fermented fermented storagestorage

11

EVOLUTION OF " AMAT" and " A2"AMAT = % Soluble ProteinA2 = % Starch

Source: Dr. Jacques Eouzan. ESSAI ENSILAGE DE MAÏS 2001/2002- CENTRALYS

CS data from France….some of the first published research showing this effect

y = 0.0507x + 46.765

R2 = 0.9432

y = 0.0424x + 47.846

R2 = 0.882245

50

55

60

65

0 50 100 150 200 250 300

TIME (days) IN STORAGE

(%)

A2

AMAT

q

20% increase in Starch

Digestibility

30% increase in 3-hr STRD in corn silage stored for 2 months vs. 10 months in study reported at 2006 Dairy Science meetings

Source: J. Dairy Sci. Vol. 89, Suppl. 1. 2006 ADSA/ASAS Annual Meeting abstracts.

1.6% units per month increase in 12-hr STRD in corn silage study reported at 2008 Dairy Science meetings

Nebraska study looking at the rate of in situ (ruminal) DM Nebraska study looking at the rate of in situ (ruminal) DM digestion of digestion of HMCHMC of varying moistures and time in storageof varying moistures and time in storage

40

60

80

100

DM

D, %

Higher ensiling moistures increases in situ digestibility

24%28%

30%

35%

0

20

40

0 56 112 168 224 280 336 392

Ensiling Period (days)

ISD

DryRolled

(only one point because it

never changedover time like

fermented corn)

24%

Source: J.R. Benton, G.E. Erickson, and T.J. Klopfenstein U of NE, Lincoln. Abstract # 936 2004 ASAS/ADSA Sessions, St. Louis, MO

24% moisture HMC is a “safe” feed but you give up the feed efficiency that can be captured with higher moisture HMC.

280 days ensiled vs. ensiled only 60 days 28% recon – 30% higher30%HMC – 8% higher35% recon – 14% higher

Results from 2005 HMC (27% moisture, processed through tub-grinder with a ¼” screen) analyzed for 12-hr in vitro STRD comparing a

(saved-frozen) 60-day (fall) sample against a 200-day (spring) sample (both samples incubated in the same in vitro run)

If a cow was receiving 10 lbs DM from this HMC, her rumen would theoretically

be exposed to: 4.6 lbs of starch (10*.68*.68) in the Fall, increasing to 5.7 lbs by Spring (10*.68*.85)

0

5

10

15

20

25

30

35

40

45

50

2002 2003 2004 2005 2006

Harvest Year (October through September)

So

lub

lilit

y o

f H

igh

Mo

istu

re C

orn

Pro

tein

, %

A factor contributing to “spring acidosis”, besides increasing STRD in CS, is the loss of buffering capacity when cows expel CO2 from panting during heat stress, increased drooling which reduces saliva flow to rumen and increased urinary bicarbonate excretions.

Hoof trimmers are the busiest in September….the result of acidosis in spring and summer!

I factor in a 2% unit increase in corn silage ruminal STRD I factor in a 2% unit increase in corn silage ruminal STRD per month of storage with a starting point of about 70%per month of storage with a starting point of about 70%