Heterosis and heterosis retention for measures of female productivity of cattle of diverse biological types

Abstract

Breeding, calving and weaning records of cows produced in a diallel of Angus, Brahman, Hereford, Holstein and Jersey were used to characterize these breed types for measures of female productivity. First-generation crossbred females were 35 d younger (P<.05), 18 kg heavier (P<.05) and 2.0 cm taller (P<.01) at first calving than contemporary straightbreds; however, these two groups did not differ for number of services. Second-generation crosses were 16 kg heavier (P<.05) and 2.4 cm taller (P<.01) at first calving than second-generation straightbreds; differences between these two groups for number of services and age at first calving were nonsignificant. Brahman and Brahman crosses tended to exhibit the longest gestation length and calving interval during the inter se phase, but were intermediate for calving interval during the terminal cross phase. Average F₁ and F₂ heterosis estimates for gestation length and calving interval were small and nonsignificant. Second-generation crossbred calves exceeded contemporary straightbreds by.97 kg (P<.01), .34 cm (P<.01) and .15 cm (P<.05) for birth weight and shoulder and hip width, respectively. Estimates of F₃ heterosis for birth characters were nonsignificant. Estimates of average maternal heterosis retained were significant for shoulder and hip width. No differences were detected (P >.05) for birth characters of terminal cross calves out of crossbred and straightbred dams. Holstein cows weaned the largest calves during both phases of this study; Jersey weaned the smallest inter se calves while Hereford weaned the smallest terminal cross calves. Estimates of F₂ heterosis were 14.7 kg (P<.01), 2.10 cm (P<.01) and 9.7% (P<.01) for weaning weight and height and survival to weaning, respectively. Average F₃ heterosis estimates were significant for weaning weight and height while average maternal heterosis retained was significant for weaning height. Calves out of F₁ dams were significantly larger at weaning than calves out of straightbred dams. Crossbred females accumulated 1.63 more (P<.01) calves and 92.3 kg more (P<.05) calf weaning weight by 12 yr of age and 30.7 kg more (P<.01) weight per year of life than straightbreds. These results demonstrate the importance of breed and heterotic effects for the characters studied.