Title: Pre-breeding ß-hydroxybutyrate concentration influences conception date in young postpartum range beef cows Authors
Submitted to: Western Section of Animal Science Proceedings
Publication Type: Proceedings
Publication Acceptance Date: June 1, 2012
Publication Date: July 15, 2012
Citation: Mulliniks, J.T., Kemp, M.E., Endecott, R.L., Cox, S.H., Scholljegerdes, E.J., Geary, T.W., Petersen, M.K. 2012. Pre-breeding ß-hydroxybutyrate concentration influences conception date in young postpartum range beef cows. Western Section of Animal Science Proceedings 63:10-15. Interpretive Summary: Changes in blood metabolites and metabolic hormones during early lactation, resulting from body weight loss after calving, can act as signals to allow or inhibit reproduction. Serum metabolite differences during early lactation were an effective means to segregate cows based on classification of young beef cows according to their conception date. This study indicates that elevated ß-hydroxybutyrate concentrations prior to breeding are related to or may have a detrimental effect on the interval to resumption of estrus in young beef cows and thereby prolong time of conception. A decreased concentration of ß-hydroxybutyrate resulted in an earlier conception date in young lactating beef cows. Therefore, ß-hydroxybutyrate concentrations prior to breeding may be a useful predictive indicator of days to resumption of estrus and conception date. In addition, chute-side measurement of ß-hydroxybutyrate concentrations may provide producers opportunity to manage cows differently to improve overall reproductive efficiency.
Technical Abstract: Cows in a negative energy balance after calving often have reduced reproductive performance, which is suggested to be mediated by metabolic signals. The objective of this 3-yr study was to determine the association of serum metabolites, resumption of estrus, milk production, cow BW change, BCS, and calf performance on conception date in 2- and 3-yr-old beef cows (n = 131) grazing native range at the Corona Range and Livestock Research Center. Cows were classified by conception date in a 60-d breeding season as early conception (EC; conceived in the first 15 d of breeding) or late conception (LC; conceived during the last 45 d of breeding). Date of conception was calculated from the following year calving date. Starting d 30 postpartum, blood samples were collected twice/wk for progesterone analysis to estimate days to resumption of estrus and serum metabolite analysis. As a chute-side measure of nutrient status and glucose sufficiency, whole-blood '-hydroxybutyrate (BHB) concentrations were measured 2 wk prior to breeding. Whole-blood BHB and serum glucose concentrations were lower (P < 0.04) in EC cows than LC cows. Serum insulin concentrations were greater (P = 0.03) in EC cows relative to LC cows. Serum NEFA and urea N concentrations were not different (P > 0.32) by cows classified by conception date. The initial calving date during the year of the study was not different (P = 0.19) between EC and LC cows. The interval required for resumption of estrus after calving was shorter (P = 0.04) in EC cows, which is expected due to treatment classification. Milk production was not different (P = 0.28) between EC and LC cows. Cow BW and BCS and were not different (P > 0.12) at any period between EC and LC cows. Calf weaning (205-d) BW was not different (P = 0.67) by date of conception. This study indicates that elevated BHB concentrations prior to breeding is coupled with prolonged postpartum anestrus in young beef cows as measured by a delayed time of conception.