Genetic Parameters among Production, Carcass Composition and Carcass Quality Traits of Beef Cattle

Production, carcass composition and carcass quality data measured on 679 grade Hereford steers raised on 18 private ranches in South Dakota were used to obtain estimates of heritability for the traits and to obtain estimates of genetic correlations among traits. The results indicate that final weight (adjusted yearling weight in breeding stock) should be the single most important trait in a selection program aimed at improving the production and carcass traits studied. The heritability estimate of 85% for final weight indicates that considerable progress can be made for this economically important trait through mass selection. In addition, desired improvement in weaning weight, daily gain and carcass muscling could be expected because of the high positive genetic correlations between final weight and these traits. Selection for final weight would result in little change in marbling and only a slight decrease in dressing percent, carcass grade, lean color and lean firmness. Visual appraisals such as conformation score and muscling score did not appear useful as predictors of animals genetically superior in the production or carcass traits studied. Nonsignificant year × sire within ranch interactions for all traits except percent kidney fat indicate that sires can be evaluated on the basis of one progeny test. The relative importance of years, ranches and sires as sources of variation in the traits measured were also studied.