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., Roberts, A.J., Waterman, R.C., Geary, T.W., Scholljegerdes, E.J., Petersen, M.K. 2012. Assessment of serum IGF-I and ß-hydroxybutyrate concentrations on reproductive performance prior to calving and breeding in young beef cows grazing native range. Western Section of Animal Science Proceedings 63:185-188. Interpretive Summary: Metabolic adaptation to body weight loss after calving has the potential to influence timing of conception in range beef cows. This study indicates that serum BHB and IGF-I concentrations may be practical indicators of conception date prior to calving in young beef cows grazing cool-season native range. Rapid chute-side measurements prior to calving of BHB may be a potential tool to provide producers an opportunity to manage potentially late conception cows differently to improve overall reproductive efficiency and collapse their subsequent calving dates. Therefore, young beef cows grazing native dormant range that conceive earlier in the breeding season have an improved adaptive mechanism to body weight loss from the metabolic stress of lactation shown by decreased circulating ß-hydroxybutyrate and increased IGF-I concentrations in the blood.
Technical Abstract: Metabolites involved in the metabolic adaptation to negative energy balance may have the potential to regulate timing 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 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 conception date in a 55 ± 2 d breeding season as early conception (EC; conceived in first 15 d of breeding) or late conception (LC; conceived during the remaining breeding season). Date of conception was calculated from the following year calving date. Blood samples were collected 30 ± 1 d prior to calving and 14 ± 1 d prior to breeding for analysis of serum IGF-I and '-hydroxybutyrate (BHB) concentrations. Conception date for EC cows were 33 d earlier (P < 0.01) than LC cows. Sampling time did not interact (P > 0.10) with conception date classification group for either serum metabolite. Cow age × conception date interaction (P = 0.04) occurred for serum BHB concentrations. Serum BHB concentrations were similar (P > 0.10) for 2-yr-old cows relative to their conception date classification. However, serum BHB concentrations were greater (P = 0.05) for LC rather than EC in 3-yr-old cows. Serum IGF-I concentrations were greater (P < 0.01) for EC cows relative to LC cows. Body condition score and cow BW were not different (P > 0.43) at calving and breeding between EC and LC cows. Calf birth BW was not different (P = 0.25) for EC and LC cows. However, calf weaning (205-d) BW was greater (P < 0.01) for LC cows relative to EC cows, indicating a difference in milk production. This study indicates that serum BHB and IGF-I concentrations may be practical indicators of conception date prior to breeding in young beef cows grazing native range.