Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: May 1, 2002
Publication Date: June 1, 2002
Citation: ROBERTS, A.J., JENKINS, T.G. 2002. EFFECTS OF VARYING ENERGY INTAKE AND SIRE BREED ON DURATION OF POSTPARTUM ANESTRUS, IGF-1 AND GH IN MATURE CROSSBRED COWS [abstract].JOURNAL OF ANIMAL SCIENCE SUPPLEMENT 80(Supplement 2):132.Abstract #111. Technical Abstract: Objectives of this study were to evaluate effects of sire breed (BREED; Angus, Hereford, Shorthorn, Galloway, Longhorn, Nellore or Salers) and level of daily metabolizable energy intake (DMEI; 132 or 189 kcal ME/kg metabolic BW or ad libitum) on postpartum anestrus and nutritional status in F1 cows out of Angus or Hereford dams (6 to 8 cows/BREED/DMEI). Circulating concentrations of IGF-1 and GH were determined at wk 2, 4, 8, and 14 to evaluate changes in nutritional status (i.e., high GH and low IGF-1 indicates negative energy balance). Within cow linear regressions were used to estimate intercepts and slopes for IGF-1 and GH. Analyses of variance were used to evaluate fixed effects of BREED, DMEI, and interaction of BREED and DMEI on length of anestrus, and slopes and intercepts of IGF-1 and GH. Length of anestrus was affected by DMEI in Galloway, Longhorn, and Nellore sired cows, but not other breeds. Intercept for IGF-1 was largest for Nellore (19.5), intermediate for Longhorn (16), and smallest (12 to 13) for remaining sire breeds. Intercept for IGF-1 was larger in ad libitum fed cows (16) than 189 kcal (13.7) or 138 kcal (12.7) fed cows. Slope of IGF-1 changed from a negative value (i.e., decreasing concentrations over time, indicating negative energy balance) towards a positive value as DMEI increased, but magnitude of change between levels of DMEI varied by BREED. Concentrations of GH increased at a greater rate over time in cows fed 132 kcal than cows fed 189 or ad libitum DMEI. Breed of sire influenced length of postpartum anestrus and energy balance (as predicted by IGF-1) in crossbred cows fed restricted levels of DMEI.