Morphofunctional parameters of the mammary gland of cows of different genotypes for the PGR gene

Progesterone is a regulator of the reproductive function and stimulates the development of glandular tissue of the mammary gland and milk secretion. Most of its effects are mediated by nuclear receptors, which are transcription factors. There is a limited amount of data on the frequency of distribution of genotypes and alleles of the progesterone receptor gene (PGR) and their association with morphofunctional parameters of the mammary gland in cattle, and all of them concern transboundary breeds.

The purpose of the scientific work is to study the morphofunctional parameters of the mammary gland of the Kostroma and Holstein cows of different genotypes for the PGR gene in the conditions of breeding farms of the Kostroma region. The studies were carried out in 2024–2025 on breeding first-calf cows of the Kostroma (n = 81) and Holstein (n = 26) breeds. The relationship between the genotype of the PGR gene and the morphofunctional parameters of the mammary gland was determined. It was revealed that in the studied samples of cows of the Kostroma and Holstein breeds, the most common genotype is AA of the PGR gene (distribution frequency 0.568 and 0.462, respectively). However, carriers of the rare PGRGG genotype had optimal morphological parameters for machine and robotic milking and a bath-shaped mammary gland. Also, based on results of the first lactation, it was found that in the sample of the Kostroma breed, the milk yield of carriers of the PGRGG genotype was 9.26% and 14.29% higher than that of the carriers of the PGRАА and PGRАG genotypes (p ≤ 0.5), respectively. Based on the data of the study, it was determined that carriers of the PGRGG genotype have morphofunctional parameters of the mammary gland that are preferable for machine and robotic milking, therefore it is necessary to continue research in this area on a larger number of animals and within other cattle populations.

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