Co)variance Components for Birth and Weaning Weights of Shorthorn Beef Cattle in Australia and the United States

摘要: (Co)variance components and genetic parameters for birth (BW) weaning weights (WW) of Shorthorn beef cattle in Australia (AU) the United States (US) were estimated using Restricted Maximum Likelihood. Five different uni- bivariate models used to fit both traits within each country. In Model 1, only a direct effect (a) was fitted. Models 2 3, maternal (m) added. A covariance between direct-maternal effects [cov(a, m)] ignored (model 2) or included 3). 4 5 m permanent environment (pe), allowed from model assumed cov(a,m) same manner as respectively. When ignoring effect, heritability estimates inflated differed markedly other models. The likelihood ratio test showed that best US while fittest BW WW AU, direct, maternal, total heritabilities, variance full AU (in parentheses) 0.46 (0.48), 0.09 (0.05), 0.42 (0.42) 0.00 (0.06) BW, 0.23 (0.32), 0.16 (0.09), 0.24 (0.26) 0.13 (0.10) WW, After pe fitted, estimate decreased slightly countries but re-markedly US. Estimate correlation moderately negative tended be more after fitted analysis not results univariate analysis. This yielded additive genetics correlations WW. These positive medium high correlation, which higher than Correlation breeding values others close unity. differences some indicate joint evaluation might require genotype by interaction considered.