Genetic Relationships among Growth and Carcass Traits of Beef Cattle

ANALYSES of genetic variation in beef cattle have indicated that selection for rapid growth rate should improve efficiency of gain because of the high heritability of gain (Gregory, 1969) and its favorable associations with feed conversion (Koch et al., 1963; Swiger et al., 1962; Swiger et al., 1965) and value of retail product above feed cost (Swiger et al., 1965). Differences in final weight account for 80 to 88% of the variation in weight of boneless retail trimmed beef on an age constant basis (Cundiff and Gregory, 1968). The purpose of this study was to evaluate the expected effect of selection for growth rate on composition and quality of beef carcasses and to further evaluate the genetic relationships among various indicators of carcass quality and composition and yields of retail product, fat trim and bone. The data were obtained on 503 steers in 75 sire progeny groups produced from 1961 through 1965 in the heterosis experiment involving Angus, Herefords and Shorthorns at the Fort Robinson Beef Cattle Research Station.