Study of the association of prolactin hormone gene (PRL) with milk productivity of Holstein cows

A herd of Holstein first-calf heifers was analyzed for the prolactin hormone gene (PRL) by PCR-PDRF analysis and individuals with high milk productivity were identified. Prolactin is a gonadotropic hormone that is produced in the adenohypophysis. It effects on the alveoli of the mammary gland, influencing the processes of growth and development of the alveolar and lobular structure of the mammary gland. It activates the working tissue of the gland, stimulating the synthesis and secretion of milk proteins and other milk substances. The prolactin (PRL) gene of the same name is responsible for the synthesis of this hormone, the polymorphism (SNP rs211032652) of which has two allelic variants: PRLA and PRLB. The PRLB allele was found to favor greater milk protein secretion in the mammary gland. This gene can serve as a marker gene for milk productivity and milk quality parameters of cattle, which makes it a promising candidate for identifying relationships in genetic variations. DNA samples obtained from blood samples of Holstein first-calf heifers belonging to the farm "Lenin breeding plant" of Atninsky district of the Republic of Tatarstan in the amount of 163 heads were studied. Cows with PRLBB genotype were characterized by a high degree of realization of genetic potential for economically important traits. Dairy cows of the homozygous subpopulation with the PRLBB genotype favorably differed from their counterparts with the homozygous PRLAA genotype in milk yield by 378 kg per standard lactation. Their milk was characterized by increased fat content (by 0.16 % or 26.5 kg) and surpassed their counterparts with PRLAA genotype in mass fraction and protein yield by 0.20 % and 29.3 kg, respectively.