Duration of the use of different genotypes of cows of Yaroslavl breed

The goal of the research is to study the indicators of the duration of use of cows of Yaroslavl breed with different percentage of admixture of Holstein blood. Its novelty consists in the fact that it determines the optimal parameters for adding the upgrading breed blood, taking into account the indicators of the duration of the use of cows. The work was performed on the basis of the information analytical system “Seleks” for 807 retired head of cows of Yaroslavl breed. General scientific research methods were used: monographic, statistical, and data visualization. It is established that the purebred cows of Yaroslavl breed and those with admixture of Holstein blood from 26 to 50% are used longer in the farm. For these animals, the average age of retirement was 4.59, 4.12, and 4.19 calvings, respectively. Maximum life expectancy indicators (2,371 days, 2,241 and 2,214 days) were also found for purebred cows and with those with upgrading breed blood from 26 to 50% inclusive. Characteristics of cows with the admixture of Holstein blood from 26 to 50% combine long-term use with high productivity, they show maximum life-time milk yield (19,358 and 19,310 kg of milk) and milk yield per one day of life (8.6 and 8.7 kg of milk). Consequently, the costs of raising and keeping these animals are paid off more effectively. It is established that crossing with the improving breed did not have a negative impact on the fat content in the milk of cows of Yaroslavl breed. Fat content in the milk of cows of different genotypes is higher than the breed standard of 4.00%. The research helped reveal the optimal parameters of admixture of Holstein breed (from 26 to 50%), which should be taken into account in the breeding work to improve the efficiency of dairy cattle breeding.