Estimation of environmental effects on post-weaning gain and yearling weight of beef cattle

Abstract

Records of post-weaning growth for 1134 heifers and 375 bulls from 11 Victorian beef cattle herds were analysed for the effects of sex, age of dam, age of calf, season of birth and herd/year on postweaning gain (PWG) and yearling weight (YLG WT). Age of dam had a significant effect on PWG and YLG WT for each sex, but the effect on heifer PWG was small. Suitable corrections for the effect of age of dam on heifer YLG WT were made using weaning weight adjusted for age of dam effects plus gain from weaning to yearling. Post-weaning management of young bulls and heifers was very different. Averaged over all herd/years, bulls were 37.5 per cent heavier than heifers at yearling age and grew 57.5 per cent faster between the two post-weaning dates, The environmental effects on PWG and YLG WT were therefore different for each sex. The effects of calf age and season were significant for each dependent variable except YLG WT for bulls and PWG for bulls respectively. The interaction between calf age and season was significant for heifers only.