EFFECT OF PROLACTIN (PRL) AND BETA-LACTOGLOBULIN (BLG) GENES ON DAIRY PERFORMANCE INDICATORS IN THE HIGHLY HOLSTEINIZED BELARUSIAN BLACK-AND-WHITE BREED

Abstract

The study show that for the prolactin gene (PRL), the highest milk yield for the period of 305 days of lactation was in first-calvers, cows of the second and third lactations having the PRLAB genotype. They were superior to their homozygotic herd mates on the PRLA allele by 1.2-10.7%, and on the PRLB allele by 4.2-9.4%. In terms of butterfat percentage, animals with the PRLBB genotype had higher rates, and in terms of milk protein content, animals with the PRLAB and PRLAA genotypes had higher rates. In terms of the amount of fat and protein in milk in first-calvers, homozygous individuals with the PRLAA genotype had higher rates, and in second and third lactation cows, heterozygous individuals with the PRLAB genotype had higher rates. For the beta-lactoglobulin (BLG) gene, the higher quantitative indicators for milk yield within 305 days of lactation, as well as for the content of milk fat and protein were in first-calvers with the BLGAA genotype, for the second and third lactation – animals with the BLGAB genotype.