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Estimates of Genetic and Phenotypic Parameters in Beef Cattle. I. Heritability of Growth Rate Estimated from Response to Sire Selection¹

Virginia Agricultural Experiment Station, Blacksburg

Abstract

Nineteen high-gaining bulls averaging 2.24 lb. per day and 19 low-gaining bulls averaging 1.65 lb. were selected from the 131 on test over a six-year period. The difference, 0.59 lb. per day, is slightly more than two standard deviations. The selected bulls, 22 Hereford, 12 Angus and 4 Shorthorn, were paired by breed and mated at random to equal numbers of grade Hereford cows for the progeny test. The steer progeny, totalling 192 head, were full-fed for 200 days following weaning. The heifers, 196 head, were wintered largely on roughage and were tested by gains on pasture their yearling summer.

Differences between the averages of the progenies of the high and low gaining sires were 0.1 lb. per day for the steer and 0.06 lb. for the heifers. Heritability estimates based on these differences ranged from 0.26 to 0.34 for the steers and from 0.21 to 0.26 for the heifers, depending on the weights used to adjust for differences in progeny numbers. When adjusted for differences in variance among the sires and within the progenies, i.e., when converted to standard measure, these estimates became 0.38 to 0.49 for the steers and 0.31 to 0.35 for the heifers.

¹ Contributing to Southern Regional Project S-10.