MILK PRODUCTIVITY OF BROWN SWISS COWS OF DIFFERENT GENOTYPES

Abstract

The results of studies of the genetic structure of the Brown Swiss cattle herd using marker alleles of blood groups and the coherence of individual genotypes with the milk productivity of cows are presented. The work was carried out from 2017 to 2024 on the basis of the laboratory of zootechnologies of the Federal State Budgetary Scientific Institution FRC of fiber crops and in the breeding reproductive center “Druzhba” in the Smolensk region. It was found that during this period the level of homozygosity increased by 82.8% and amounted to 19.5%, the increase in milk yield was 2191 kg. In the herd, 76.5% of the heredity of cows is controlled by seven marker EAB alleles out of 45 identified. There is an accumulation (40%) of the marker EAB allele G₃O₁T₁Y₂E^/₃F^/₂G^//₂ – 20.8% more than the breed average. The breeding value of individual EAB marker alleles and genotypes was determined. The highest milk productivity out of 1355 animals was shown by first-calf heifers with markers G₃O₁T₁Y₂E^/₃F^/₂I^/G^// (22-6739-4.31-3.15), B₁O₃Y₂A^/₁E^/₃G^/P^/Q^/Y^/ (129-5827 -4.19-3.28). In cows whose genotypes the most common allele in the herd, G₃O₁T₁Y₂E^/₃F^/₂G^//, was combined with other markers, the best genotypes in terms of their effect on the selected traits were established, for example, G₃O₁T₁Y₂E^/₃F^/₂G^//₂ // G₃O₁T₁Y₂E^/₃F^/₂ I^/G^//₂, G₃O₁T₁Y₂E^/₃F^/₂G^//₂ // B₁G₁KE^/₁F^/₂O^/. The productivity of animals homozygous for this marker exceeded the sample average, and the presence of the marker G₃O₁T₁Y₂E^/₃F^/₂G^// was found in the genotypes of 79% of the record-breaking cows of the breed, of which 21% were in the homozygous state. In terms of productive longevity, the best results among retired cows were observed in animals with the genotype G₃O₁T₁Y₂E^/₃F^/₂G^//₂//O^/; homozygous cows had lower rates of productive longevity compared to the average data for the sample.