Progress 01/01/07 to 12/31/10
Outputs
OUTPUTS: Six experiments were conducted with cattle to evaluate the impact of increasing protein deposition by various means on urea recycling, as measured by use of doubly labeled urea. Protein deposition was altered by changing supplements provided to forage-fed cattle, by evaluating different physiological states of the cattle (young vs. mature), by providing limiting nutrients (energy or amino acids), by providing cattle with a beta-agonist (zilpaterol), and by implanting the cattle with trenbolone acetate/estradiol. Data generated from this research was used by Dr. Mark Hanigan to evaluate the representation of urea kinetics in metabolic cow model (Molly) and thereby improve predictions of urea recycling in cattle. Data has been presented at meetings of the American Society of Animal Science, published in journals (some work is still in the publication process), and presented to the livestock industry through the Beef Cattle Research reports of Kansas State University. PARTICIPANTS: Principle investigators are Evan C. Titgemeyer and KC Olson. Mark Hanigan from Virginia Tech fit the data to mathematical models to extend our understanding of urea recycling. Graduate students involved in conducting these experiments were Derek Brake, Eric Bailey, and Kari Spivey TARGET AUDIENCES: Beef cattle industry, including all phases relating to cow-calf, growing cattle, and feedlot cattle. Other researchers investigating protein metabolism of ruminants. PROJECT MODIFICATIONS: There have been no major modifications to the general experimental approach.
Impacts
Data demonstrated in growing and finishing cattle that increases in body protein deposition (i.e., increased lean tissue growth) in response to beta-agonist feeding, implantation, or provision of a limiting nutrient decreased urea recycling. This suggests that diets marginal in ruminally available nitrogen may require additional supplementation of nitrogen to optimize performance when cattle deposit more protein in their bodies. Data also demonstrated that protein and energy supply to the ruminal microbes could impact the proportion of urea production that was recycled to the gut, with the responses differing somewhat between young calves and more mature cattle, likely due to the greater protein requirements of the younger calves for growth. Fitting the data to a metabolic cow model (Molly) indicated that some parameter changes to the model were needed to accurately fit the data; these included a reduction in the rate of blood urea transfer to urine, an increase in the rate constant for transfer of urea from blood into the rumen, and an increase in the rate constant for urea synthesis. All of these parameters impact urea synthesis and movement through the body. Revision of the parameters reduced prediction errors for urea production, urea returning to the gut (urea recycling), urinary urea excretion, urinary nitrogen excretion, and nitrogen retention. Ruminal ammonia concentrations were predicted with large slope bias, indicative of a model representation problem. The slope bias was negative indicating the model over-predicted ruminal ammonia responses to changes in diet. The model does not represent any regulation of ammonia absorption, but the residuals pattern suggested that ammonia absorption rates are enhanced when ammonia concentrations increase and inhibited when they decline. Reduction of absorption when ammonia concentrations are low, which is associated with low protein diets, would serve to conserve nitrogen and improve nitrogen efficiency. Such a mechanism is not encoded in either of the current beef or dairy nutrient requirement models which would lead to an over-prediction of nitrogen requirements under conditions of low dietary protein. Addressing this problem in the requirement systems would potentially reduce the need for supplemental protein for cattle on very low protein diets which would reduce nitrogen losses to the atmosphere and surface water. Overall, this research improves understanding of protein metabolism in cattle. The contribution of urea recycling to ruminal nitrogen supply can be better predicted with use of our data. By describing urea kinetics and the contribution of urea to ruminal nitrogen requirements, our research improves the ability to model nitrogen use by cattle. Data was used to evaluate and modify a metabolic cow model to better represent ammonia and urea kinetics, and therefore more accurately account for urea recycling when calculating dietary protein requirements of cattle. This should improve our ability to optimize dietary nitrogen use, reduce feed cost, and improve environmental quality.
Publications
- Brake, D.W., Titgemeyer, E.C., and Jones, M.L. 2010. Effect of nitrogen supplementation and zilpaterol-HCl on urea kinetics in steers consuming corn-based diets. Journal of Animal Physiology and Animal Nutrition, first published online: 10/29/2010 DOI: 10.1111/j.1439-0396.2010.01064.x
- Bailey, E.A., Titgemeyer, E.C., Olson, K.C., Brake, D.W., Anderson, D.E., and Jones, M.L. 2010. Effects of supplemental energy and protein on forage digestion and urea kinetics. Journal of Animal Science, 88(E-Suppl. 3): 130.
- Brake, D.W., Titgemeyer, E.C., and Jones, M.L. 2010. Effect of nitrogen supplementation and zilpaterol-HCl on urea kinetics in steers consuming corn based diets. Journal of Animal Science, 88(E-Suppl. 3): 130.
- Bailey, E.A., Titgemeyer, E.C., Olson, K.C., Brake, D.W., Anderson, D.E., and Jones, M.L. 2010. Urea recycling in beef cattle fed prairie hay-based diets. Page 78 to 81 in Beef Cattle Research Report of Progress 1029, Agricultural Experiment Station Kansas State University, Manhattan, KS.
- Bailey, E.A., Titgemeyer, E.C., Olson, K.C., Brake, D.W., Anderson, D.E., and Jones, M.L. 2010. Effects of supplemental protein and energy on digestion and urea kinetics in beef cattle. Page 85 to 86 in Beef Cattle Research Report of Progress 1029, Agricultural Experiment Station Kansas State University, Manhattan, KS.
- Brake, D.W., Titgemeyer, E.C., and Jones, M.L. 2010. Effect of nitrogen supplementation and Zilpaterol-HCl on urea recycling in steers consuming corn-based diets. Page 74 to 77 in Beef Cattle Research Report of Progress 1029, Agricultural Experiment Station Kansas State University, Manhattan, KS.
- Brake, D.W., Titgemeyer, E.C., Jones, M.L., and Anderson, D.E. 2010. Effect of nitrogen supplementation on urea recycling in steers consuming corn-based diets. Page 82 to 84 in Beef Cattle Research Report of Progress 1029, Agricultural Experiment Station Kansas State University, Manhattan, KS.
- Brake, D.W., Titgemeyer, E.C., Jones, M.L., and Anderson, D.E. 2010. Effect of nitrogen supplementation on urea kinetics and microbial use of recycled urea in steers consuming corn-based diets. Journal of Animal Science, 88: 2729-2740.
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Progress 01/01/09 to 12/31/09
Outputs
OUTPUTS: Six experiments have been conducted with cattle to evaluate the impact of increasing protein deposition by various means on urea recycling, as measured by use of doubly labeled urea. Protein deposition was altered by changing supplements provided to forage-fed cattle, by evaluating different physiological states of the cattle (young vs. mature), by providing limiting nutrients (energy or amino acids), by providing cattle with a beta-agonist (zilpaterol), and by implanting the cattle with trenbolone acetate/estradiol. Data from three of these experiments were presented at national ASAS meetings, and additional data has been submitted for presentation next year. Several manuscripts have been submitted for publication, and others are currently being prepared. Data have been provided to Dr. Mark Hanigan, who will apply the data to model development in an effort to improve predictions of urea recycling in cattle. PARTICIPANTS: Principle investigators are Evan C. Titgemeyer and KC Olson. Mark Hanigan from Virginia Tech is fitting the data to mathematical models to extend our understanding of urea recycling. Graduate students involved in conducting these experiments were Derek Brake, Eric Bailey, and Kari Spivey. TARGET AUDIENCES: Beef cattle industry, including all phases relating to cow-calf, growing cattle, and feedlot cattle. Other researchers investigating protein metabolism of ruminants. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
In finishing cattle, protein supplementation increased urea recycling, with the increases being related to the amount of nitrogen provided. Although cattle supplemented with zilpaterol consumed more protein, they did not recycle more urea, indicating that the increases in body protein deposition decreased urea recycling. This suggests that diets marginal in ruminally available nitrogen may require additional supplementation of nitrogen to optimize performance when a beta-agonist is fed. Implantation of growing calves with trenbolone acetate/estradiol tended to increase protein deposition, but to decrease urea production, urinary urea excretion, and the amount of urea recycled to the gut. This data suggests, similar to the work with beta-agonists, that products that increase protein deposition by the animal might lead to a greater dietary requirement for ruminally available nitrogen. Methionine supplementation, similar to implantation, tended to increase protein deposition and decrease urea production and urinary urea excretion. In a growing calf model where leucine was specifically designed to be limiting, supplementation with leucine increased protein deposition. Supplementation with energy also tended to increase protein deposition. Although both leucine and energy supplementation decreased urinary urea excretion, they did not affect urea production or the amount of urea recycled to the gastrointestinal tract. In young, growing calves fed prairie hay, supplementation with increasing amounts of casein led to improvements in microbial protein production and protein deposition. With increased protein supplementation, a lesser percentage of urea production was recycled to the gut. With glucose supplementation, a greater proportion of urea production was recycled to the gut than when volatile fatty acids were supplemented, likely due to greater microbial capture of nitrogen in the rumen leading to lower ruminal ammonia concentrations. In more mature cattle fed prairie hay, supplementation with increasing amounts of protein increased microbial protein production, protein deposition, urea production, and urinary urea excretion. Although ruminal glucose supplementation did not affect urea production, it decreased urinary urea excretion, particularly when provided in combination with high levels of supplemental protein. The proportion of urea production that was recycled to the gastrointestinal tract was not affected by glucose supplementation in these cattle, likely because the overall protein status of the more mature cattle was greater than that of the younger calves. This research improves understanding of protein metabolism in cattle. The contribution of urea recycling to ruminal nitrogen supply can be better predicted from our data. By describing urea kinetics and the contribution of urea to ruminal nitrogen requirements, our research improves the ability to model nitrogen use by cattle. Our data can generate models that account for urea recycling when calculating protein requirements of cattle. This contributes to development of ration-balancing software to optimize dietary nitrogen use, reduce feed cost, and improve environmental quality.
Publications
- Brake, D.W., Titgemeyer, E.C., Jones, M.L., and Anderson, D.E. 2009. Effect of nitrogen supplementation on urea kinetics and microbial use of recycled urea in steers consuming corn-based diets. J. Anim. Sci. 87(E-Suppl. 2):341.
- Bailey, E.A., Titgemeyer, E.C., Olson, K.C., Spivey, K.S., Brake, D.W., Anderson, D. E., and Jones, M.L. 2009. Effects of supplemental energy and protein on forage digestion. J. Anim. Sci. 87(E-Suppl. 2):155.
- Spivey, K.S., Titgemeyer, E.C., and Jones, M.L. 2009. Effect of energy source on leucine utilization and nitrogen retention in growing steers. J. Anim. Sci. 87(E-Suppl. 2):154.
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Progress 01/01/08 to 12/31/08
Outputs
OUTPUTS: Animal work has been completed on five separate trials. Nitrogen retention, a measure of lean tissue growth, was altered by changing nutrient inputs and by feeding zilpaterol or providing trenbolone acetate/estradiol implants. In cattle fed diets based on rolled corn, zilpaterol increased nitrogen retention. Supplementing diets with either dried distiller's grains or with urea increased nitrogen retention, and responses were greater with distiller's grains than with urea. In calves fed prairie hay, increasing the amount of supplemental ruminally degradable protein increased nitrogen retention. For the forage-fed calves, provision of ruminal glucose did not improve nitrogen retention, likely due to a negative effect of ruminal digestion of the forage, and provision of volatile fatty acids into the rumen had negative effects on nitrogen retention, likely due to reductions in forage intake and digestion. For steers fed diets based on soybean hulls and maintained under conditions where leucine supplies were deficient, leucine supplementation increased nitrogen retention; in contrast to previous observations, these calves did not have large responses in nitrogen retention when energy was supplemented either as glucose to the abomasum or as volatile fatty acids to the rumen. Neither the implantation of lightweight calves with trenbolone acetate/estradiol nor supplementation with methionine led to significant increases in nitrogen retention, but numeric improvements were observed to both. As a whole, these studies contained a number of treatments that altered the dietary supply of nitrogen to the rumen microbes, the energy supplies to ruminal microbes and to the animal, as well as the nitrogen retained by the animal. The effects of these alterations on urea recycling will be evaluated in samples collected from all of these trials using dually labeled urea. PARTICIPANTS: Evan C. Titgemeyer - Principle investigator K. C. Olson - Principle investigator TARGET AUDIENCES: Beef cattle industry, including all phases relating to cow-calf, growing cattle, and feedlot cattle. Other researchers investigating protein metabolism of ruminants. PROJECT MODIFICATIONS: Procedures involving animal use appear to be working appropriately, and there are no major modifications expected to the general experimental approach.
Impacts
Our research is intended to address a deficiency in our understanding of protein metabolism by cattle. Dietary nitrogen that is conserved via urea recycling contributes to the metabolizable protein supply of cattle. It does so when it is incorporated into microbial cell protein, which subsequently fulfills a portion of the animal's protein requirement. The extent to which urea recycling contributes to ruminal nitrogen supply and animal protein requirements is unknown. By improving our ability to model urea recycling in cattle, we will improve our ability to optimize animal production, to formulate diets that do not exceed nitrogen requirements, and to effectively provide specific limiting nutrients (e.g., amino acids) to more precisely meet animal requirements. By describing urea kinetics and the contribution of urea to meeting the ruminal nitrogen requirements of cattle, our research will improve our ability to model nitrogen use by cattle. In particular, our data can be used to account for urea recycling when calculating the protein requirements of cattle. This will contribute to development of ration-balancing software that optimizes dietary nitrogen use, reduces feed costs, and improves environmental quality.
Publications
- No publications reported this period
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Progress 01/01/07 to 12/31/07
Outputs
OUTPUTS: Animal work was completed and/or is currently underway on several projects, but no data is yet available because the collected samples have not yet been completely analyzed. Specifically, projects evaluating the impact of a beta-agonist on urea recycling have been completed, and a project to evaluate the impact of ruminal vs. intestinal energy supply on urea recycling is underway. The group of cattle being used for the energy-supply study will also be used for a study evaluating the impact of implants. So far, procedures involving animal use appear to be appropriate for achieving our goals.
PARTICIPANTS: Evan C. Titgemeyer - Principal investigator, K. C. Olson - Principal investigator
TARGET AUDIENCES: Beef cattle industry, including all phases relating to cow-calf, growing cattle, and feedlot cattle
PROJECT MODIFICATIONS: Procedures involving animal use appear to be working appropriately, and there are no major modifications expected to the general experimental approach. Projects were somewhat delayed in their initiation due to the last-minute failure of a supposedly committed graduate student to enroll at the university.
Impacts
Our research is intended to address a deficiency in our understanding of protein metabolism by cattle. Dietary nitrogen that is conserved via urea recycling contributes to the metabolizable protein supply of cattle. It does so when it is incorporated into microbial cell protein, which subsequently fulfills a portion of the animal's protein requirement. The extent to which urea recycling contributes to ruminal nitrogen supply and animal protein requirements is unknown. By improving our ability to model urea recycling in cattle, we will improve our ability to optimize animal production, to formulate diets that do not exceed nitrogen requirements, and to effectively provide specific limiting nutrients (e.g., amino acids) to more precisely meet animal requirements. By describing urea kinetics and the contribution of urea to meeting the ruminal nitrogen requirements of cattle, our research will improve our ability to model nitrogen use by cattle. In particular, our data can
be used to account for urea recycling when calculating the protein requirements of cattle. This will contribute to development of ration-balancing software that optimizes dietary nitrogen use, reduces feed costs, and improves environmental quality.
Publications
- No publications reported this period
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