Abstract
The article presents the results of the productive indicators of Holstein cows depending on the polymorphism of the kappa-casein gene and their belonging to lines Vis Back Ideal and Reflection Sovereign in the conditions of the breeding reproducer of LLC "Barmino", Lyskovsky municipal district of Nizhny Novgorod region. The degree of realization of the ge-netic potential of productive indicators of cows is determined based on the assessment of the proband itself, its ancestors, on the basis of which the indices are calculated. It has been established that the polymorphism of the kappa-casein gene and the lineage of cows affect the productive performance of animals. It was revealed that the studied animals surpass their female maternal ancestors in milk yield; in the analysis of variance, the degree of influence of mothers on the milk productivity of daughters was 0.39–0.45, and that of fathers' mothers was 0.32-0.33. In the conditions of this breeding farm, the genetic potential in milk yield of the daughters of the Vis Back Ideal line has been most fully realized and reached 111.6 %. It has been proved that with the highest milk productivity of bull mothers and the lowest productivity of cow mothers, animals with the CSN3AA genotype give the best milk values among their peers for other CSN3 genotypes, which confirms the influence of paternal and maternal ancestors on the level of realization of genetic potential.