Abstract
Birth and livability data on 995 calves born, weaning data on 915 calves and carcass data on 817 calves produced in two calf crops were studied. Calves were sired by 51 bulls from 18 Angus herds and 44 bulls from 18 Polled Hereford herds (two to four sires sampled/herd) through AI matings to Hereford and Angus cows at the U.S. MARC. Estimates of genetic variance did not differ significantly between breeds. From pooled analyses, effects of herd origin of sires were significant for birth weight, 200-day weight, postweaning average daily gain, 452-day weight, marbling, final carcass grade and carcass conformation grade. Effects of sire/herd were highly significant for postweaning average daily gain, 452-day weight, carcass conformation, final grade, marbling, fat thickness, longissimus muscle area and significant for estimated cutability. Genetic variance components for herds and sires/herd were used to compute the intraherd correlation of individual breeding values. Relatively higher correlations for growth traits (averaging .51) than for carcass traits (averaging .16) indicate that selection pressures and responses have been more diverse, among herds, for growth traits than for carcass traits. Copyright © 1975. American Society of Animal Science . Copyright 1975 by American Society of Animal Science.