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., Roberts, A.J., Waterman, R.C., Geary, T.W., Scholljegerdes, E.J., Petersen, M.K. 2012. Assessment of serum IGF-1 and ¿-hydroxybutyrate concentrations on reproductive performance prior to calving and breeding in young beef cows grazing native range. Western Section of Animal Science Proceedings. 90(Suppl. 3):324. Abstract No. T201. Technical Abstract: Metabolites involved in the metabolic adaptation to negative energy balance may potentially contribute to regulation of reproductive success. Therefore, the objective of this 4-yr study was to determine the association of serum metabolites, cow BW, BCS, and calf performance on conception date in spring calving 2- and 3-yr-old beef cows (n = 381) grazing native range at the Fort Keogh Livestock and Range Research Laboratory. Cows were classified by subsequent calving date in a 55 ± 2 d breeding season as either conceiving early (EC; conceived in first 15 d of breeding) or late (LC; conceived during the remaining breeding season). Blood samples were collected in two periods 30 ± 1 d prior to calving and 14 ± 1 d prior to breeding to determine circulating concentrations of IGF-1 and B-hydroxybutyrate (BHB). Assignment to conception group resulted in a mean conception date that was 33 d earlier (P < 0.01) in EC than LC cows. Cow age × sample period × conception date interaction (P < 0.01) occurred for serum BHB concentrations. Serum BHB concentrations were similar (P > 0.10) for 2-yr-old cows regardless of their conception date classification and sampling period. However, pre-calving serum BHB concentrations were greater (P < 0.01) for LC than EC in 3-yr-old cows with no difference (P = 0.86) at pre-breeding. Serum IGF-1 concentrations were greater (P < 0.01) for EC cows relative to LC cows at pre-calving and pre-breeding sampling periods. Cow BW and BCS were not different (P >_ 0.43) at pre-calving or pre-breeding between EC and LC cows. Calf BW at birth was not different (P = 0.25) between EC and LC cows, but EC cows weaned lighter (205-d BW; P < 0.01) calves, suggesting more energy may have been diverted from milk production toward reproduction in EC cows. This study indicates that pre-calving serum concentrations of BHB and IGF-1 may be indicative of their capacity for subsequent rebreeding. Chute-side measurements of these factors may provide producers opportunity to manage cows differently to improve overall reproductive efficiency.