Genetic association between stayability, and productive and reproductive traits in Holstein cows

The objective was to estimate the genetic parameters for the cow's ability to stay in the herd (stayability) until 48 and 54 months of age (STAY48 and STAY54) and up to 36 and 48 months after the first calving (STAY36ac and STAY48ac), and their associations with 305-day milk production (MP305) in the first lactation, age at first calving and first calving interval, from the first three lactations of cows reared in Brazil and born between 1987 and 2006. The covariance components were estimated by bivariate analyses, using the Bayesian approach. The a posteriori distributions of the components of interest were obtained with the Gibbs sampler. Fixed effect of contemporary group, additive and residual random genetic effect, and age of dam as covariate (linear and quadratic) were included in the analyses. Low heritability values were obtained for most traits, except for STAY48ac and MP305. Genetic correlation estimates between age at first calving and stayability traits were high and positive, except for STAY48ac. In addition, we detected genetic correlations between MP305 and STAY36ac and STAY48ac. In conclusion, we can infer that genetic correlations between MP305, and STAY36ac and STAY48ac indicate that the current focus on selection of animals for improved milk production in the first lactation can lead to genetic gains on longevity, although not expressive.