Estimation of genetic parameters for milk production traits in Czech dairy cattle populations

Multiple-trait analyses treating the yields in the first three lactations as different traits were performed for milk, fat and protein yield for the populations of the Holstein and Czech Pied breeds kept in the Czech Republic. Data sets from the national milk recording data base were used. Five subsets of data were formed for each breed because the overall data sets were very large. The total number of animals with lactation records was 738 488 for Holstein and 1 016 388 for Czech Pied breed. Variance and covariance components were estimated with VCE using REML under an animal model. The model for the analyses included the factors herd-year-season (fixed), animal (random), calving age, days open and calving interval (covariables). The estimated heritabilities for milk yield were higher for Holstein (0.28 to 0.30) than for Czech Pied cattle (0.21 to 0.26). They were slightly higher than the heritabilities for fat and protein yield. A genetic correlation near one was found between the yields for the second and third lactations.