Genetic determination of milk productivity traits in Holstein cows of German origin

The Holstein cattle breed is one of the best breeds, but its breeding faces many difficulties in Russian conditions. The paper presents the results of evaluating the genetic determination of breeding traits in Holstein breed dairy cows in German conditions. The evaluation was carried out based on the pedigrees of Holstein heifers brought to the Kaluga Region. The authors studied the productive traits of maternal and paternal ancestors, including milk yield, percentage of fat and percentage of protein in milk, as well as heritability coefficients, coefficients of phenotypic (rРР), genetic (rАА) and environmental correlation (rЕЕ), evaluated the difference in milk producing ability of proband cows in comparison with that of mothers in 4 groups with the milk yield of at least 8,000 to 12,000 kg of milk, and estimated the degree of influence of the fathers' breeding value (EBV), based on daughters' milk yield, on the implementation of milk productivity traits in proband cows. It was found that with a low breeding value of fathers, the mothers’ genotype determined breeding traits to the extent of 11.6 (% of protein) to 31.9% (fat in kg), and fathers were responsible for 1.3 to 9.2% in the determination. In the sample, the heritability of breeding traits was 34.2%, of which the "ancestor" factor accounted for 9.1%, the fathers' EBV accounted for 15.3%, and the combined effect of these factors accounted for 9.8%. External factors determined the implementation of milk productivity traits to the extent of 65.8%. Based on the research carried out, it was concluded that the phenotypic manifestation of genetic correlation has a complex multiplicative nature of the interaction between genes and the interaction between the genotype and external factors.