LAUSR

Abstract The aim of this work was to determine the dependency between polymorphism in the PRL locus g.8398G > A and fertility rates, bodyweight of cows and calves, the course of parturition and viability of calves in Polish Black-and-White Holstein-Friesian cattle. Three genotypes (AA, AG, and GG) were identified with a frequency of 0.0293, 0.3672 and 0.6035. The frequency of the G and A alleles was respectively, 0.7871 and 0.2129. There was a significant dependency between the genetic variant in locus g.8398G > A of the PRL gene and age at first insemination, age at first calving, insemination index, length of pregnancy, length of the dry period and weight of male calves after parturition. The AA homozygotes were characterized by more favorable values of selected reproduction indices; the cows of that genotype and male calves coming from these animals were characterized by the lowest weight after parturition.