Heritability and Repeatability of Weaning Weight in Beef Cattle1

Abstract

The records of 1915 purebred Hereford and 436 purebred Angus calves, representing the progeny of 120 bulls from 20 private herds, were analyzed in estimating heritability of weaning weight. The data were adjusted for differences in age and sex of calf and age of dam. The weaning weights of 866 calves from 378 cows were analyzed in estimating repeatability of weaning weight. Data were adjusted for year differences, and the variance among dams was calculated on a within-ranch basis. The influence of sire on weaning weight was highly significant for both breeds. Estimates of heritability and the standard error for Hereford, Angus and the combined breeds were 0.33±0.08, 0.32±0.16 and 0.32±0.07, respectively. The mean square for the variance among dams within ranches was highly significant for both breeds. Repeatability of weaning weight was estimated as the intraclass correlation of adjacent weaning weight records of the same cow. Estimates of repeatability and the standard error for Hereford, Angus and the combined breeds were 0.42 ±0.04, 0.52 ±0.13, and 0.42 ± 0.04, respectively.