Correlation between exterior traits and milk productivity of Holstein cows

Purpose. Identification genetic and phenotypic correlations between the main traits of milk productivity and exterior conformation in a verified population of Holstein cattle. Materials and Methods. The subject of the scientific research was a verified dataset of 64 536 Holstein cows, extracted from the IAS «SELEKS‑Milk» database. Evaluation of selected traits — exterior conformation and milk productivity — was carried out according to the Eurasian Economic Commission (EEC) methodology [11]. To assess the components of phenotypic variability of the traits, multifactorial analysis of variance (ANOVA) was applied. When estimating the values of breeding‑genetic parameters of the studied population, basic procedures of the quantitative trait theory were applied [12]. Results. Genetic correlations between the studied trait groups and their practical significance for dairy cattle breeding have been established: the trait height shows a positive genetic correlation with milk yield (rg = 0.21), milk fat (rg = 0.24), and milk protein (rg = 0.22) in kilograms; chest width exhibits virtually no genetic association with major productivity indicators (rg ≈ 0.07−0.08); body conformation type demonstrates a weak genetic relationship with milk yield, fat, and protein (in kg) (rg ≈ 0.1−0.11); the trait rear udder width shows a positive correlation with major productivity traits (rg = 0.25); front udder length exhibits moderate positive correlations with milk yield (rg = 0.16), fat (rg = 0.17), and protein (rg = 0.16) in kilograms; rear udder attachment height demonstrates moderate positive genetic correlations with milk yield (rg = 0.17), fat (rg = 0.18), and protein (rg = 0.17) in kilograms; udder depth shows virtually no association with major productivity traits (rg ≈ 0.06−0.08). Conclusion. The data obtained on milk productivity and exterior traits of Holstein dairy cattle bred in the Russian Federation can be used to develop equations for weighting coefficients of sub‑indices and for constructing a comprehensive breeding index.