Submitted to: Western Section of Animal Science Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: June 1, 2012
Publication Date: July 16, 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 Abstract 90(Suppl. 3):148. Technical Abstract: Cows in 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 subsequent calving date. Beginning on d 30 postpartum, blood samples were collected twice/wk for serum metabolite analysis and progesterone analysis to estimate days to resumption of estrous cycles. As a chute-side measure of nutrient status and glucose sufficiency, whole-blood B-hydroxybutyrate (BHB) concentrations were measured 2 wk prior to breeding. A random subsample of cows from groups was mechanically milked approximately 57 d postpartum. 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) between EC and LC cows. Initial calving date during the year of the study was not different (P = 0.19) between EC and LC cows. The postpartum anestrous interval was shorter (P = 0.04) in EC cows, indicating that the earlier conception was due partially to an earlier return to cyclicity. 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) between EC and LC cows. This study indicates that blood BHB concentrations prior to breeding may provide a sensitive indicator of energy status for rebreeding success in young beef cows as measured by interval to conception.