Abstract
Data from 3,462 Hereford calves were analyzed. Birth weight and preweaning daily gain were 7 to 8% higher in bulls than in heifers. Heritabilities of traits were consistently smaller for bulls than for heifers. The heritabilities, giving bulls first and heifers second, were: birth weight, 49 and 57%; daily gain to 135 days, 15 and 17%; daily gain to weaning, 13 and 21%; 200 day weight, 15 and 25% daily gain postweaning, 29 and 65%; and 452 and 550 day weight, 23 and 52%. Genetic and phenotypic correlations among traits were presented. Birth weight was more closely correlated with postweaning daily gain (rG=0.42 and 0.30, rp=0.31 and 0.34 for bulls and heifers) than it was with preweaning daily gain (rG=0.10 and 0.28, rp=0.18 and 0.27 for bulls and heifers). Preweaning daily gain was not closely related with postweaning gain in bulls (rG=0.14, rP=0.15). In heifers the genetic correlation between pre and postweaning gain was much higher (rG=0.47) than the phenotypic correlation (rp=0.07). These results indicate differential weight should be given to bull or heifer records in assessing genetic merit of individuals or parents. Copyright © 1973. American Society of Animal Science . Copyright 1973 by American Society of Animal Science.