Influence of Holsteinization on the biological productivity and genotypic structure of the simmental breed

The research was carried out on the Simmental breed. The reproductive crossing with red Holstein was implemented for their improvement. This made it possible to increase the milk productivity of first-calf cows in the herd during 5 years by 1130 kg, the fat content was increased by 0.17%, and the protein content was increased by 0.12%, in comparison with purebred Simmentals. More than half of the herd has the bloodline of 51-74%, low-blood crossbreeds make up 4.9%. The highest milk yield is observed in caws with the bloodline of 75% (7612 kg), which is higher than the extreme values of the bloodline: by 602 kg with the highest the bloodline (75% or more) and by 820 kg with low-blood animals (up to 25%). In the process of its Holsteinization, the ratio of genotypes CSN3 and BLG changed. The frequency of CSN3^AA increased from 40.7 to 74.2%, and the frequency of CSN3^BB decreased from 15.2 to 1.8% compared to purebred Simmentals. The fluctuation of the BLG^BB frequency from 27.5 to 39.2% was noted. The breeding and genetic parameters of the herd are at the level: Ca is 59.2; N^a is 16.0; V is 54.4%; χ² is 0.000-3.360. In 2015, heterozygous purebred Simmentals with BLG^AB had a higher milk productivity, and the fat content of caws BLG^BB by 415 kg and 0.09%, respectively, in comparison with carriers of alternative genotypes. In 2020, among Holsteinized Simmentals, caws with BLG^BB have a priority position, the milk productivity of which is 493.6 kg higher than with the BLG^AB genotype.