MANAGEMENT TECHNIQUES TO REDUCE NITROGEN LOSSES FROM FEEDLOT

CATTLE

S. L. Archibeque, J. Ham, H. Han and M. M. Kappen

Colorado State University, Fort Collins, CO

Purpose of Study

Participants in the initiative include the Colorado Department of Public Health and Environment Air Pollution Control Division, U.S. EPA Region 8 Air Program, the Air Resources Division of the National Park Service and the U.S. Forest Service

Alternatives producers have to decrease nitrogenous excretions: Feed less protein (can be problematic)

This study aimed to utilize approved technologies that improve muscle accretion without hindering productivity

Hypothesis: Ractopamine, with or without steroidal

implants, may lessen nitrogenous excretions in yearling feedlot cattle by stimulating a shift of body accretion to lean tissue rather than adipose

USDA Awards National Food and Agriculture Grant

Objective

To determine if Ractopamine HCl with and without Trenbolone acetate/estradiol benzoate implants lessens nitrogenous excretions from yearling crossbred feedlot cattle

Study Design

Balance Trial Completely randomized block design 24 Hereford x Angus cross steers were put

into 4 treatment groups with 2 replications:

ControlOptaflexx (ractopamine

hydrochloride) 430 mg/hd/day for last 42 days feeding period topdressed

Synovex-Plus Implanted (200 mg of trenbolone acetate and 28 mg of

estradiol benzoate)

Combination of Optaflexx and

Synovex-Plus Implant

2 x 2 factorial arrangement of

treatments

Materials and Methods

Agriculture Research, Development and Education Center (AREDEC) Wellington, Colorado

36 Hereford x Angus crossbred steers Initial BW: 235 kg 204 days on feed Initially housed in large drylot pens; 6 head per

pen to facilitate halter breaking Transitioned through 5 step-up rations

Materials and Methods

Steers trained to balance trial procedures Day 137 steers were randomly selected from the

trained group of cattle and blocked into heavy and light group classifications

Within each group, steers were stratified by weight to achieve equal weights within treatment groups

Materials and Methods

Implanted 48 days prior to start of balance trial

Implant used: Synovex-Plus (IMP) (200 mg trenbolone acetate and 28mg of estradiol benzoate, Fort Dodge Animal Health) Heavy Group:

Implanted on day 137 Light Group:

Implanted on day 144

Materials and Methods

Steers were individually fed RAC treatment groups received premix with 400 mg

x hd-1x d-1 of Optaflexx (Elanco Animal Health) in 449.6 g ground corn and controls received 449.6 g ground corn

Heavy Group: RAC topdress began on day 164

Light Group: RAC topdress began on day 171

Methods: Data Collection

Balance Trial Animals were weighed upon entry

and exit of metabolism barn Heavy group entered

metabolism barn on day 185 Light group entered

metabolism barn on day 192

Collections occurred over a 6 day periodTotal urine, fecal excretions, feed offered

and refusals were collected, weighed and 10% subsample was retained for analysis

Methods: Sample Analysis

Dry Matter (DM) Fecal and feed samples: 60˚C until 2

consecutive dry weights were obtained

Nitrogen (N) LECO

Urine Urea Nitrogen (UUN) Stanbio Laboratory BUN Enzymatic

Endpoint

Methods: Statistical Analysis PROC MIXED in SAS

Completely randomized block design with a 2x2 factorial arrangement of treatments.

Fixed effects: IMP, RAC, IMPxRAC, Random effects: Block Steer was experimental unit

Results

Implanted steers fed Ractopamine tended to have lower DMI compared to other treatments (IMPxRAC; P< 0.09)

N intake (P>0.11) and fecal N (P>0.18) were not different due to treatment, yet numerically reflected the trend noted for DMI

Results

Urinary N excretion was decreased by feeding Ractopamine (P<0.01) Implanted steers receiving Ractopamine tended

(IMPXRAC; P<0.08) to excrete less urinary N than steers receiving Ractopamine only (20 g vs 5 g reduction/d)

Steers fed Ractopamine had a decreased urine urea N excretion (P<0.02) (12.5 g/d, )

N retention was not affected by treatment (P>0.14)

Summary

Results indicate that urinary N excretion can be reduced by incorporating Ractopamine according to labeled usage during the final phase of the finishing period

This effect may be enhanced by implant status of the feedlot steers

More studies will be required to elucidate the potential interactions of beta-agonists with implant status, timing of implantation, and types of implants

Implications

Based on the results of the study, use of beta-agonists during the finishing period would result in a 650 kg reduction in urinary N excretion during each day from a 50K head feedlot.

Urinary N is the primary source of ammonia emissions from feedlots.

Other methods of managing N

Phase feeding Adjusting N provision with stage of growth Providing less N as cattle mature and shift

growth from lean tissue to adipose deposition

Oscillating protein Creates a gradient of protein in the

digestive tract Stimulates “urea recycling

Problems Ration adverse feedlot systems

Potential for future mitigation Methodology must be relatively cheap

and not impair performance Most effective methods should be either

capable of continual use or rapid adaptation to meet a specific temporal concern

Linkages with early warning systems “Spot” reductions in N emissions Aggressive use of implants during

Spring? New labeling for beta-agonists?

Questions?