Modification of the allelofund of the Brown Swiss cattle breed during its improvement

The results of changes in the quantitative and qualitative genetic structure of the Brown Swiss cattle breed of the Smolensk region, controlled by marker genes of blood groups, for the period from 1975 to 2020 are presented. The statistically significant difference in the frequency of occurrence between individual alleles ranged from +0.32 to – 0.13 (p?0.001), with the exception of the I1Y2 and B1G1KE/1F/2O/ alleles (p?0.01). The index of genetic similarity between the animals of the original population bred in 1975 and the animals of the new generation born in the period 2016-2020 has a low value and is 0.52. The homozygosity coefficient doubled and amounted to 13.8. The main influence on the formation of the breed's allelofund is exerted by breeding bulls, whose genetic potential, estimated by the milk productivity of mothers, increased by 215.4 kg of milk fat compared to 1975. Currently, the most widespread animals in the breed are marked with EAB alleles: G3O1T1Y2E/3F/2, B1O3Y2A/1E/3G/P/Q/Y/, G1O/, B1P1Y2G/Y/, b, I1Y2E/1G/I/G//, B1G2KY2E/1F/O/G//. To further improve the productive qualities and increase the competitiveness of the breed, it is necessary to maintain genetic diversity among animals using marker.