APPLICATION OF DIAGNOSTICS RESULTS OF B- AND K- CASEINS GENETIC POLYMORPHISM
Enhancing innovation in dairy cattle breeding is interesting for not only dairy manufacturers, but also milk processing enterprises and suppliers of various raw materials. Application of DNA technologies allows improving efficiency of cattle breeding for genetically determined milk quality characteristics to produce specialized products, reduce costs and time achieving goals. In addition to the traditional selection of animals, identification of gene variants, which are preferred for selection, allows to carry out selection according to genotype. The study of the stock of Holstein breed in Belgorod region reveals that milk of cows with the BB and AB genotypes of к-casein had significantly better characteristics for cheese making compared to milk of cows with homozygous A-allele of к-casein: increased yield of cheese grain on dry matter / protein by 13-17%, reduced amount of normalized and raw milk for the production of 1 kg of curd grain by 12.5%. There was no difference in the suitability of milk for cheese manufacture between cows with heterozygous and homozygous genotypes for the allele B of the к-casein gene. An investigation of large group of Holstein cows (n=8706) showed low (8.46%) proportion of animals that homozygous for the allele B of the к-casein gene and high proportion of heterozygotes and homozygous(AA) animals (46.88 %).Genotyping of bulls (n=84) reveals that animals with homozygotes for the desirable alleles of к-casein were 7.1%, for β-casein - 22.6%.The deficit of native Holstein bulls with the desired genotypes today can be compensated by imported bovine semen from countries in which selection is carried out not only for ß- and к-caseins, but also for all factors influencing milk suitability for cheese manufacture. The high proportion (38.87%) of homozygous cows for the A<sub>2</sub> allele in the presence of a significant number of livestock, allows forming a specialized herd for the production of «hypoallergenic» milk. A significant proportion of heterozygous к-casein genotypes makes it possible to create groups / herds of cows with the К-casein B allele according to the genotyping results and to receive «improved» milk for cheese making.