Evaluation of the Distribution Frequency of the Variants of Allelic Polymorphism in the BoLA-DRB3 Exon 2 Using RFLP-PCR

BoLA-DRB3 is a part of the major histocompatibility complex characterized by more than 100 polymorphic sites within the exon 2. This gene is associated with immunological traits and resistance or susceptibility to various diseases as well as with productive traits and milk quality in cattle. The purpose of the study was a primary evaluation of the allelic polymorphism in BoLA-DRB3 exon 2 in the Ural region using nested PCR and RFLP-PCR. The objects of the study were Holstein cows ( n = 55). Restriction fragment lengths were determined by the agarose gel electrophoresis. According to the BoLA-DRB3.2 genotyping, the most common genotypes were *23/*24, *24/*24, *16/*16, *24/*28, and *9/*38 (distribution frequency from 8.9 to 26.5%); other genotypes (*24/*38, *24/*9, *2/*37, *16/*26) were characterized by a lower distribution frequency. The majority of identified alleles (*2, *9, *26, *37, *38) in the studied sampling were earlier proven to be neutral. In the studied population, the genomes associated with the susceptibility or resistance to the leukemia virus were revealed in 56 and 29% of animals, respectively; 15% of animals were characterized by a neutral genotype. Based on these results, one can conclude about the necessity of genetic screening of cattle populations for the BoLA - DRB3 polymorphism, especially in regions that are epidemiologically unfavorable in relation to leukemia. The obtained data can be used in breeding programs to enrich cattle herds with alleles associated with the resistance to the bovine leukemia virus.