Relevance. The genotype of the animal plays a significant role in realizing its productive potential, along with other factors affecting dairy productivity. Marker-oriented breeding (MAS) of cattle, which utilizes genetic markers associated with economically valuable traits, has gained popularity in the last two decades. One such marker is the thyroglobulin (TG) gene, which is involved in the production of a thyroid prohormone.

Methods.The research was conducted on cows of Kostroma and black-and-white breeds at breeding farms in the Kostroma region. Genetic material was obtained from the tail vein of the cows using individual vacuum systems with an anticoagulant. The polymorphism of the TG gene (rs135751032) was determined using RT-PCR and detection by hybridization-fluorescence method. The results were processed using biometric analysis and calculation of population-genetic indicators.

Results. In the populations of cows of the Kostroma and black-and-white breeds of the Kostroma region, the predominance of carriers of the CC genotype and the C allele of the thyroglobulin gene was established. At the same time, among cows of these breeds, there is a tendency to higher milk productivity in heterozygous animals. The nature of the associative relationship between TG genotypes and milk productivity indicators differed significantly for each individual herd. This indicates the need to study TG in combination with other DNA markers of milk productivity and metabolism. Statistically significant differences between cows of different TG genotypes were found only in full-aged animals, which perhaps indicates the prospects of using TG to determine the genetic potential of productive longevity of cows.