THE INFLUENCE OF THE BREED AFFILIATION OF BULLS ON THE MICROSTRUCTURE OF THE SKIN
The article presents the results of the assessment of the development of the skin of the red steppe bulls (I group), Simmental (II group) and Kazakh white-headed (III group) according to the seasons of the year. At the same time, the total thickness of the skin and its individual layers, the diameter of collagen fibers, and the development of the glandular apparatus were determined. The results of histological studies of the skin indicate an increase in the thickness of the epidermis, the pilar and reticular layers of the skin, as well as the diameter of collagen fibers in the summer compared to the winter season, which is due to the growth and development of animals. There was also an increase in the depth of hair follicles, sebaceous and sweat glands with a decrease in their number in bulls of all genotypes. At the same time, the advantage of bulls of the Kazakh white-headed breed in the development of all structural elements of the skin was noted. So the gobies of the Red Steppe and Simmental breeds were inferior to them in the thickness of the epidermis in the winter period, respectively, by 2.2 pm (7.14%) and 1.1 pm (3.45%), the polar one - by 62.5 pm (6.13 %) and 24.9 pm (2.36%), reticular - by 314.5 pm (15.04%) and 117.3 pm (9.13%), total skin thickness - by 379.2 pm (12 .07%) and 143.3 pm (4.24%). Similar intergroup differences in the thickness of individual skin layers and its total thickness were also noted in the summer season. Bulls of the Kazakh white-headed breed were also distinguished by a greater thickness of collagen fibers and a better developed glandular apparatus of the skin, which was reflected in more hair, sebaceous and sweat glands per 1 mm<sup>2</sup>.