Genetic characteristics cows of Brown Swiss breed depending on the reasons for culling from the herd

The productive longevity of cows has an impact on the economics of milk production. Currently, there is a decrease in the culling age of cows, which negatively affects the payback of funds spent on their cultivation. Premature culling is influenced by paratypical and genetic factors. The aim of our research was to study the genetic characteristics of dairy cows that were dropped out of the herd for various reasons at a young age, using marker genes of the EAB locus of blood groups. The cows of the Brown Swiss breed on Smolensk-type numbering 766 heads in 2001-2021, culled at the age of 9 years and younger, who were divided into groups for reasons for culling studies were conducted. The animals in winter are keep confined, in summer are keep camp-pasture. Blood groups of animals were determined using their own standardized reagents, genotypes were established by family analysis. The main reasons for the culling were: low milk productivity (21.41%), diseases of the reproductive organs (19.59%), udder diseases (14.49%), difficult calf birth and complications (8.88%), yeldness (7.70%), leg diseases (7.31%). In total 58 EAB alleles in 766 cows were found, but in groups, depending on the reasons for culling, their number was 27-40. Significant genetic similarity (r > 0,8) was found between groups of animals that were eliminated for various reasons, but differences were found in the frequency of occurrence of individual EAB alleles that were statistically significant for markers: G3O1T1Y2E`3F`2, b, G1O`, B1O3Y2A`1E`3G'P'Q'Y`. The most specific markers of the EAB locus for each group of animals were determined, depending on the reasons for culling.