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ARS Home » Plains Area » Clay Center, Nebraska » U.S. Meat Animal Research Center » Nutrition, Growth and Physiology » Research » Publications at this Location » Publication #329214
Title: Uterine environment and pregnancy rate of heifers with elevated plasma urea nitrogen

Author
item AMUNDSON, OLIVIA - South Dakota State University
item LARIMORE, ERIN - South Dakota State University
item McNeel, Anthony
item Chase, Chadwick - Chad
item Cushman, Robert - Bob
item Freetly, Harvey
item PERRY, GEORGE - South Dakota State University

Submitted to: Animal Reproduction Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/28/2016
Publication Date: 8/29/2016
Citation: Amundson, O.L., Larimore, E.L., McNeel, A.K., Chase, Jr., C.C., Cushman, R.A., Freetly, H.C., Perry, G.A. 2016. Uterine environment and pregnancy rate of heifers with elevated plasma urea nitrogen. Animal Reproduction Science. 173:56-62. doi: 10.1016/j.anireprosci.2016.08.011.

Interpretive Summary: Diets high in protein are associated with lower reproductive performance and changes in the uterine environment. The objective of this study was to determine the effect of elevated systemic concentrations of urea nitrogen on the uterine environment, oocyte quality, and pregnancy success in beef heifers. Heifers were randomly assigned to one of two dietary treatments: 1) Control (10% CP) or 2) High protein (14% CP). Uterine pH, plasma urea nitrogen (PUN), ammonia, and glucose concentrations were determined on day 7 of a synchronized estrous cycle. Pregnancy status was determined by ultrasonography 30 days following the breeding season. In vitro fertilization was performed on heifers precluded from uterine analysis to determine the effect of a High Protein diet on oocyte quality. Plasma urea concentrations were greater in the High Protein diet compared to Control; however, there was no effect of diet on plasma ammonia, plasma glucose, uterine pH, interval to estrus, duration of estrus, or pregnancy rate. There was no effect of diet on the number of oocytes collected, number of oocytes cleaved, amount of blastocysts, percentage of oocytes cleaved and percentage of blastocysts present. In summary, high nitrogen diets increased PUN concentrations in heifers; however, there were no deleterious effects on reproduction. Dietary protein levels were within the expected protein levels of grass pastures during a spring breeding season suggesting that under normal conditions, dietary protein should not negatively affect reproduction in beef heifers. Higher protein intake can result from pastures high in legumes, or through preferential selection of plant species that are high in protein which would exceed the range of protein that we fed and could result in poor fertility.

Technical Abstract: Diets high in protein are associated with lower reproductive performance and changes in the uterine environment. The objective of this study was to determine the effect of elevated systemic concentrations of urea nitrogen on the uterine environment and pregnancy success in beef heifers. Heifers (n = 150) were matched by breed, age, and body weight then randomly assigned to one of two dietary treatments: 1) Control (10% CP) or 2) High protein (14% CP) over three replicates (n = 40/replicate). Estrus was synchronized with an injection of '"PGF" '_2a. Uterine pH, plasma urea nitrogen (PUN), ammonia, and glucose concentrations were determined on d 7 of the estrous cycle. Pregnancy status was determined by ultrasonography 30 d following the breeding season. In vitro fertilization was performed on heifers precluded from uterine analysis (n = 15/diet) to determine the effect of a High Protein diet on oocyte quality. Plasma urea concentrations were greater in the High Protein diet compared to Control (P < 0.001). There was no effect of diet on plasma ammonia (P = 0.12), plasma glucose (P = 0.40), uterine pH (P = 0.67), interval to estrus (P = 0.54), duration of estrus (P = 0.38), or pregnancy rate (P = 0.83). There was no effect of diet (P > 0.40) on the number of oocytes collected, number of oocytes cleaved, amount of blastocysts, percentage of oocytes cleaved and percentage of blastocysts present. In summary, high nitrogen diets increased PUN concentrations in heifers; however, there were no deleterious effects on reproduction.