Estimation of Genetic and Maternal Effects in Crossbred Cattle of Angus, Charolais and Hereford Parentage. II. Postweaning Growth, Ribeye Area and Fat Cover

Abstract

Linear functions of means of breed combinations were used to estimate genetic and maternal effects of the Angus (A), Charolais (C) and Hereford (H) breeds. Data from 637 animals were used to estimate an additive effect for each breed, individual and maternal heterosis for each two-breed combination, and maternal and grand maternal effect for each breed. Additive effects of C, H and A were 136, −18 and −118 g/day, 12.5, −6.8 and −5.7 cm2 and −.71, .30 and .41 cm for postweaning daily gain, ribeye area and fat cover, respectively. A × H cross produced a positive individual heterosis effect of 3.5, 1.9 and 13.0% for daily gain, ribeye area and fat cover, respectively. No significant individual heterosis effects were found in the C × H cross. A × C cross had positive heterosis of 1.6 and 3.0% for daily gain and ribeye area, respectively. All crosses produced negative (−2.1 to −3.3 cm2) maternal heterosis effects on ribeye area. Maternal heterosis for postweaning daily gain was 38, 19 and −5 g/day in A × C, A × H and C × H crosses, respectively. Total maternal effects of C were .17 cm for fat cover, −43 g/day for postweaning daily gain and −3.8 cm2 for ribeye area and differed (P<.01) from the total maternal effects of both H and A. H differed from A (P<.05) only with regard to daily gain. In each case, total maternal effects possessed the opposite sign to that of additive effects. Adjustment to a constant carcass weight reduced additive effects on ribeye area while additive effects for fat cover increased in absolute magnitude. Adjustment of the carcass traits to constant carcass weight decreased individual heterosis in ribeye area by 70%. Expected means of all possible two-breed and three-breed rotations through eight generations were calculated using the genetic and maternal constants for ribeye area.