INFLUENCE OF GENOTYPE ON PRODUCTION TRAITS OF DAIRY COWS
In recent decades in the Russian Federation the improvement of dairy cattle to increase productive and breeding qualities is carried out by crossbreeding with the highly productive Holstein breed. A significant amount of foreign pedigree material in the improvement of breeding and production traits of Russian dairy cattle breeds contributes to the constant variability of the population genetic structure, which requires continuous observation and study to improve the effectiveness of breeding. The purpose of the research is to study the productive features of first-calf cows of different genotypes and their interrelation with the proportion of Holstein blood in modern populations of Kholmogory, Russian Black Pied and Yaroslavl breeds. We conducted the research using the data of the analytical system “SELEX” - dairy cattle on breeding farms of the Vologda Oblast. The analysis of first-calf breeding cows in terms of the proportion of Holstein blood revealed that 99.7% of animals of the Russian Black Pied breed have a different proportion of blood, Kholmogory - 99.3%, Yaroslavl - 92.4%. We have found that there is a direct positive correlation between milk yield and blood degree (r = 0.23) (P ≤ 0.001) in the Russian Black Pied cows. The Kholmogory first-calf cows have an increase in milk yield when blood admixture is not more than 50%, then the productivity declines. In the population of the Yaroslavl breed, the milk productivity of cows increases along with blood admixture up to 75%. Crossbreeding the Russian Black Pied breed population with Holstein does not worsen the quality indicators of milk. In the populations of Kholmogory and Yaroslavl breeds with an admixture of Holstein blood of more than 50%, we have found a decrease in the indicators of the fat and protein mass fraction in the milk of cows. The results obtained should be taken into account in further breeding with the populations.