In the process of animal adaptation to changing environmental conditions, the hair cover, which is known to perform a heat-protective function primarily, plays a significant role. The hair cover of animals undergoes changes depending on the season of the year and the natural and climatic zone in which the animals live. It has its peculiarities in different species (breeds). The nature and features of the hair cover of animals are often used by scientists to compile zoological systematics, assess the health and constitution types of animals, their acclimatisation ability, etc. In this article, the authors reviewed age-related changes in weight, size, thickness and tightness of animal skins (changes in skin thickness from the ridge to the floor) and features of the hair cover of the skin’s yaks of Northern Tajikistan. The authors also noted that in all animals, the weight of hides increases in proportion to the rise in live body weight. The absolute importance of skins, up to the age of half a year of yaks, is almost two times higher than cattle. In yaks at one- and three years old, the thick- ness of skins at the standard point in these animals is somewhat comparable. But the thickness of the pelts in the collar and area of hiding yak next to the floor remains higher by about 25-40%. Yaks are known to have three main categories of hair: long hairs (in the abdominal region of the hide and on the tail), short hairs (on the rump, neck and back) and down inches (in all parts of the animal’s fur). Long coats are also the thickest. The hair length of newborn yaks is 187.60±2.66 mm, of one-year-old yaks 452.50±2.52 mm, and of six-year-old yaks, it reaches 475 mm. The authors determined the total amount of hair of different categories in the three topographic parts of the body: in the rump, the sum of hair is 1545 hair units; in the collar part, the sum of hair is 1590 hair units; in the abdominal area of the body the sum of hair is 1770 hair units. The collar and rump do not have long hairs, unlike the abdomen. Downy hairs are characteristic of all parts of the hide but predominate in the scruff and collar. The dynamics of age-related changes in the hair cover of yaks have been determined.
Physiological and morphological changes in facial skin with aging. (I). Age-related changes in the skin of Japanese women.