Comparison of models to estimate genetic effects of weaning weight of Angus cattle.

摘要: Weaning weights from nine sets of Angus field data three regions the United States were analyzed. Six animal models used to compare two approaches account for an environmental damoffspring covariance and investigate effects sire × herd-year interaction on genetic parameters. Model 1 included random direct maternal genetic, permanent environmental, residual effects. Age at weaning was a covariate. Other fixed age dam herd-year-management-sex combination. Possible influence dam's phenotype her daughter's ability modeled by including regression (f m ) (Model 3) or fitting grandmaternal 5). Models 2, 4, 6 based 1, 3, 5, respectively, additionally (SH) With estimates f ranged -.003 to.014, (co)variance similar those 1. heritability from.02 to.07. Estimates direct-maternal correlation (r am increased compared with SH, fraction phenotypic variance due SH .10. smaller r greater than without Likelihood values showed that more important The comparisons suggest may be biased downward if and(or) are not in weight.