The Influence of Breed Composition on Weaning Weight Parameters in a Multibreed Beef Cattle Population

Direct and maternal components were estimated for birth weight and weaning weight in a multibreed cattle population. Data consisted of 20840 records of calves with varying levels of British (B), Charolais (C), Simmental (S) and Afrikaner (A) breeds. It included several F1, backcrosses, threebreed and fourbreed crosses, having an approximate average composition of /8B : /8S : /8C : /8A. The number of calf, sire and dam genotypes were 122, 33 and 43, respectively. Single and twotrait analyses were conducted fitting an animal model. Direct and maternal variance components were estimated. The direct (ha), and maternal (h 2 m) heritabilities and genetic correlation between direct and maternal effects (ram) for weaning weight were 0.55, 0.22 and –0.53 for the single trait and 0.53, 0.20 and –0.60 for the two-trait analyses, respectively. In a subsequent analysis, where direct and maternal breed proportions as well as direct and maternal average heterosis were additionally included, corresponding estimates were 0.37, 0.18, -0.42 and 0.41, 0.18 and –0.46, respectively. Charolais had a positive direct but negative maternal effect and Simmental a negative direct but positive maternal effect. The British breeds had a positive direct but strong negative maternal effect, while the Afrikaner had a large negative direct but small positive maternal effect.