Morphological adaptation features of yakut horses to extreme temperatures in the Arctic

This article presents the results of the study of adaptive changes in hair cover in horses of Yakut breed of different populations, which contribute to the improvement of thermal insulation qualities in winter. In the study, it was found that horses of the Momsky population, in the period of severe cold weather, have the highest values of winter hair mass per 1 cm2 of skin (0.107 g) compared to the Amginsky population (0.070 g). In the first year of horses' life, hair growth is most intense and hair length reaches adult values by the age of 6 months. In Momsky horses, hair length is 37.5±0.5 mm and in Amginsky horses it is 46.0±0.68 mm. Long winter hair has adaptive value for foals of both populations. In summer, the average hair length in Amginsky foals is 5.54±0.04 mm, and in Momsky foals it is 6.0±0.8 mm. In the first winter, intensive hair growth is observed in Yakut horses, and the number of hairs per 1 cm2 of skin reaches the values of 1443±108 pcs/cm2 in Amginsky foals and 1812 ± 127 pcs/cm2 in Momsky foals. In summer, the thickest hairs with a diameter of about 53.4±1.40 μm were observed in Momsky foals and 53.1±1.0 μm in Amginsky foals. In winter, young foals from Mom ulus have absolute hair thickness values that are higher than those of young foals from Amga ulus. In winter, the thinnest hairs were observed in the Amginsky young stock, 55.3±1.2 µm, and in the Momsky young stock, 57.9±1.31 µm. In general, these results confirm the high thermal insulating ability of the hair coat in Yakut horses, which is an adaptation to the cold climate in Yakutsk horses.