Estimate of genetic parameters of conformation traits, milk production and age at first calving in dairy Gyr breed cows

Data from 573 primiparous lactating Gyr cows were used to estimate the (co) variance components of the conformation traits, milk production up to 305 days of lactation (NIP) and age at first calving (AFC) by REML method. These components were used to calculate heritability coefficients and genetic, phenotypic and residual correlations. The conformation measures, the heart girth (HG), croup height (CH), body length (BL), teats length (TL), teats diameter (TD) and udder height (UH) were obtained in the cows at first lactation with average age of 4.05 years. The genetic and phenotypic correlations between NIP and AFC were 0.49 and 0.18 respectively. The genetic correlation between traits were NIP x HG = -0.37; PP x CH = -0.62; MP x BL, = -0.52; MP x TL = -0.08; MP x TD = -0.12; MP x UH = -0.69; AFC x HG= -0.05; AFC x CH = -0.37 and AFC x BL = 0.25. These estimates of genetic correlation between milk production and body size measures, in general, indicate that the selection for milk production held as a correlate response, decreasing in the cow size.