The role of the prolactin gene in the formation of morphofunctional features of the mammary gland and predisposition to mastitis in Kostroma cows

The main functions of the prolactin hormone in mammals are mammogenesis, lactogenesis and galactopoiesis, which serves as the basis for searching for associations of the PRL gene genotypes with the parameters of the morphofunctional characteristics of the mammary gland of cows, but such data are not presented in open sources of literature on cattle. The aim of the study: to analyze the associative links of the prolactin gene with the formation of morphofunctional features of the mammary gland and predisposition to mastitis in Kostroma cows. The study was conducted in 2024-2025 within the framework of the RSF Grant on breeding first-calf heifers of the Kostroma breed (n = 81) in the Kostroma region. The animals were assessed for morphofunctional parameters of the mammary gland, milk was analyzed for somatic cell content, mastitis was diagnosed and the genotype was determined by the prolactin gene. The study found that the PRL^AG genotype (0.481) had the highest frequency in the sample of Kostroma cows. It was also found that among the Kostroma cows, mastitis was most often recorded in individuals with the PRL^GG genotype (in 25% of cases). However, the assessment of cows using the case-control model did not show a reliable association between the prolactin gene genotype and the fact of mastitis development in animals (P=0.7112). At the same time, the carriers of the PRL^G allele were distinguished by the better development of some exterior features related to suitability for machine milking, in particular, the development of the posterior lobes, the shape and severity of the udder fold, which indicates the development of glandular breast tissue. Nevertheless, carriers of the AA genotype tended to have a higher milk yield – by 12.93% compared to heterozygotes, and by 9.05% compared to cows of the PRL^GG genotype. The results indicate a complex nature of the effect of the locus in question on the signs of mammary gland development and the need for further research with a larger number of animals in the sample and the studied marker genes.

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