Estimates of genetic parameters for growth traits of Mexican Charolais cattle

Charolais calf records provided by the Mexican Charolais Breeders Association for an eight year period (1997-2005) were analyzed to estimate genetic and phenotypic parameters for birth weight (n = 30,821), weaning weight adjusted to 205 d (n = 39,556), and postweaning gain (n = 21,831). Estimates of (co)variance components were obtained by REML with an EM algorithm and single-trait animal models. Maternal permanent environmental effects were unimportant for birth weight and postweaning gain and were not included in the final model. Estimates of direct heritability were 0.22, 0.33, and 0.45 for birth weight, adjusted weaning weight and postweaning gain, respectively. Estimates for the corresponding maternal component were 0.16, 0.17, and 0.14. Estimates of total heritability and direct-maternal genetic correlation were 0.12 and -0.65, 0.16 and -0.72, and 0.20 and -0.84 for birth weight, adjusted weaning weight and postweaning gain, respectively. For adjusted weaning weight, the estimated maternal permanent environmental variance (28.93 kg(2)) accounted for 4% of the estimated total phenotypic variance (765-43 kg(2)). Expected response to single-trait selection for growth traits of Mexican Charolais cattle would be lessened due to highly negative direct-maternal genetic correlations.