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?