Heredity and variability of selection traits of black-and-white cows under conditions of transformation by the Holstein breed

In the selection of the Black-and-White breed over the past 20 years, Holstein stud bulls have been actively used, the genotype of which has actually absorbed the Black-and-White breed at the present time. At certain stages of absorption, the effectiveness of selection caused contradictions. These contradictions remain up to nowadays. Black-and-White cattle with an average Holstein bloodline of 56.5% were used as an object of the research. The data of zootechnical records, cards of breeding cows of the farm, which lactated in the period from 2010 to 2016 in the Michurin SPC, were used as primary information. To determine the effectiveness of selection, we conducted these studies. It was established that the herd had heritability coefficients (h2) of the most important productive traits acceptable for selection (h2 = 0.38-0.42). The minimum milk yield of the mothers of the evaluated cows was 2222 kg of milk for 305 days of lactation, the maximum was 7464 kg of milk. At the same time, the daughters showed a minimum milk yield of 2141 kg of milk, the maximum was 10101 kg of milk, however, the variability of milk yield decreased from 23.4 to 20.1% (n=471). In terms of milk fat content, the distribution of mothers was from 3.40 to 3.98%, and in daughters it was from 3.01 to 4.96%. The variability increased from 2.42 to 4.77%. In terms of milk protein content, the distribution of mothers was from 2.78 to 3.56%, and in daughters it was from 2.81 to 4.15%. The variability, as well as the fat content of milk, increased from 6.11 to 7.83%. The live weight of the cows varied from 406 to 700 kg (Cv=5.7%), the milk yield rate - from 0.970 to 4.410 kg / min (Cv= 18.8%). Daughters surpassed their mothers by 22.3% in milk yield for 305 days of lactation, by 22.7% in milk fat in kg and by 21.5% in the amount of protein in milk in kg from the value of traits, which confirmed the high degree of implementation of traits and the influence of the absorption process by Holsteins on productive traits. These data also show the relative value of heterosis. In the herd, the number of cows with high milk yields increased per generation, and the maximum of them exceeded 10,000 kg of milk. The Holsteinization process has influenced the increase in fat and protein content in milk, the variability of selection traits, the rate of milk yield, etc.