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Heritability and Repeatability of Weaning Weight in Beef Cattle¹

South Dakota State University, Brookings

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.

¹ Department of Animal Science, published with the approval of the Director of the South Dakota Agricultural experiment Station as Publication No. 641 of the Journal Series. Cooperative with A.R.S., U.S.D.A., and a contribution from Regional Project NC-1, Improvement of Beef Cattle through Breeding Methods.

² This paper represents part of a thesis submitted by the senior author to the Graduate Faculty of South Dakota State University as partial fulfillment of the requirements for the degree of Master of Science.

³ Appreciation is extended to Henry P. Holzman, Associate Animal Husbandman Emeritus. South Dakota State University Extension Service, for making the data available for this study.