Abstract
Environmental and genetic effects on preweaning growth traits were evaluated for 4034 calves born and 3732 calves weaned in second and later parities from contemporary populations of first-cross dams maintained at two locations, Brandon and Manyberries. The calves were sired by Chianina (Chi), Charolais (C), Limousin (L) and Simmental (S) bulls mated to 10 F1 dam crosses representing the Hereford × Angus (HA) and nine dam-cross combinations produced by matings of C, S and L sires with H, A and Shorthorn (N) females. Sex differences were important (P < 0.0001) with males averaging 7% heavier at birth and 5% higher in measures of postweaning growth than females. Location differences were negligible for birth weight (1.2%), but preweaning growth rate was 10–13% greater at Brandon (P < 0.0001) than at Manyberries. Year differences were large for all traits measured (P < 0.0001) and, with the exception of birth weight, were related to differences in annual weaning date. Progeny rankings by terminal sire breed were Chi > C (2.5%), Chi > S (4.2%), and Chi > L (11.4%) for birth weight (all P < 0.0001) and Chi = C = S > L by 6% (P < 0.0001) for all measures of preweaning growth. Ranking of the dam crosses by their breed of sire (DS) were C > S > L for birth weight (P < 0.0001) and S > C > L for preweaning growth (P < 0.0002). The paired DS comparisons indicated S > L by 9.1% and C > L by 2.7% for growth rate. Ranking of the dam crosses by their breed of dam (DD) were H = N > A (P < 0.0001) for birth weight and [Formula: see text] for preweaning growth traits. A location × dam cross interaction was evident for the Charolais × Shorthorn dam cross (P < 0.01). Progeny from all dam crosses except the LH and LA at Manyberries grew more rapidly than their contemporary controls (HA progeny) with the Simmental crosses averaging 11–14% higher than the HA. Genetic interactions involving breed of sire and breed of dam were absent. Key words: Beef cattle, crossbreeding, preweaning growth
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