ASSOCIATION OF CSN2 AND CSN3 CASEIN GENE POLYMORPHISM WITH MILK PRODUCTIVITY IN SIMMENTAL COWS

Abstract

The genetic structure of a herd of Simmental cows was studied at the breeding reproducer base of FSBEI HE Vavilov University at the kappa–casein (CSN3) and beta–casein (CSN2) loci to assess the influence on economically valuable traits. Genotyping was carried out by the polymerase chain reaction method with restriction analysis performed on a sample of 60 animals. Statistical processing included calculation of allele frequencies, verification of Hardy–Weinberg equilibrium by χ² criterion, determination of inbreeding coefficient (Fis) and assessment of the significance of differences using Student’s t‑test. Population equilibrium was established for both loci (χ² CSN3 = 3.62; χ² CSN2 = 3.85; P > 0.05). An excess of heterozygous individuals was revealed (Fis CSN3 = –0.268; Fis CSN2 = –0.447), indicating the absence of inbreeding. Animals with heterozygous genotype AB at the CSN3 locus significantly exceeded AA homozygotes in milk yield by 321.73 kg (3874.93 versus 3553.20 kg, P <0.05) and protein yield by 12.33 kg. The excess in fat yield amounted to 10.09 kg. At the CSN2 locus, the best parameters of fat yield (146.46 kg) and protein (111.64 kg) were recorded in carriers of the A1A1 genotype. Cows with the A2A2 genotype had the lowest milk yield (3581.00 kg) and protein yield (102.34 kg). The results confirm the feasibility of using DNA markers in selection and breeding to develop herds with high protein milk production. The introduction of genotyping will allow optimizing pair selection and increasing the economic efficiency of milk production in the Saratov region.