Influence of Dam's Milk Production and other Factors on Post-Weaning Performance and Carcass Characteristics of Hereford Cattle

Abstract
Three year's data were analysed by least squares regression analyses to study the effects of dam's milk production, three levels of pre-weaning nutrition, sire, sex, age and weight of dam, and birth order of calf on five post-weaning performance characteristics of 129 calves and four carcass characteristics of 98 of the 129 calves. Increases in the dam's 240-day milk production were associated with the progeny's increase in stocker gains, small decreases in fattening gains and significant increases in weight per day of age at slaughter, slaughter weight and slaughter grade. Increases in weaning weight due to increases in milk production continued to be present, almost to the pound, at slaughter. Differences in pre-weaning nutrition did not greatly affect stocker and fattening gains but significantly influenced weight per day of age at slaughter, slaughter weight and slaughter grade. Differences in weight between the best and poorest pre-weaning nutrition groups were greater at slaughter than at weaning; 150 vs. 117 lb., respectively. Post-weaning performance was not significantly influenced by differences due to sires, age of dam or weight of dam. Late born calves had fattening gains and weight per day of age at slaughter significantly higher than those of calves born early in the season. However, early born calves had significantly higher slaughter weights than late born calves. In the carcass studies, increases in 240-day milk production and improvement in pre-weaning nutrition were associated with significant increases in carcass weight. No significant negative association of these pre-weaning treatments on carcass conformation grade or rib-eye area was found. Other than sex, the only remaining important effect on carcass traits was the significant sire effect on rib-eye area. An important observation from the correlations was the consistent negative association of rib-eye area per cwt. of carcass with all other post-weaning and carcass variables.