Inbreeding in selection herds Brown Swiss breed

A characteristic of a herd of Brown Swiss cattle is given according to the degree of homozygosity using marker genes, the level of inbrednes, and the influence of inbreeding on economically useful traits is determined. The research was carried out in the breeding farm of the Smolensk region from 2017 to 2023 (n = 1454 heads) on animals of the brown Swiss breed with records in pedigrees confirmed by genetic examination, 23% of them are inbred to varying degrees. Generally accepted zootechnical and immunogenetic methods were used in data processing. The degree of homozygosity of inbred cows was 18.7 – 32%, and outbred cows 16.1%. The proportion of homozygous cows in the EAB locus of blood groups in the inbred group (15.3%) was 2.2 times higher than in the outbred group. Inbred cows, on average, turned out to be more precocious, superior in milk productivity to outbred and their mothers (with the exception of protein milk), but inferior in productive longevity to outbred animals. Cows obtained as a result of long–term inbreeding, in relation to the other groups, had a higher proportion of homozygous animals (17.3%), a high degree of homozygosity (23.6), showed better productive qualities, but the period of productive longevity turned out to be shorter compared to outbred ones by 3 lactation, and by 0.7 lactation - with an average for all Inbred. It is recommended to use related mating of a distant degree, control the level of homozygosity and avoid inbreeding of a close degree to further increase the dairy productivity of cows in the herd.