Age variability of mammary gland histostructure in dairy and non-dairy animals of different breeds and origin

Abstract

Increase in milk production and improvement of milk quality must be addressed, along with of paratypic factors, through further researches of breast morphology and physiology. These studies are targeted not only at its morphological and functional characterization, but also at establishing basis for changing the body's activities and improvement of dairy animals. For most dairy breeds in the process of breeding almost reached the biological threshold of productivity. In addition, with the development of highly mechanized and automated technologies for milk production, the requirements for the selection of animals for adaptation to such conditions, in particular for the state of the udder, have increased. Therefore, an additional reserve can be the improvement of dairy cattle and improve the quality of milk on the basis of in-depth studies of the morphological, functional characteristics and physiology of the breast. The most informative data are presented on the structure and function of the udder in species with high initial milk yield and high quality indicators in comparison to the most common breeds of cattle. In the scientific literature there are no comparative data on histological mammary gland of cows and female-yaks. The results presented by us in this study fill this gap. Investigations of histostructure of udder in cows were carried out on black-motley and Brown Swiss breeds and their crosses with Holsteins (F1 and F2, Lenin APS Farm), and on the local population of Brown Swiss cows and female-yaks imported from Tuva and Kyrgyzstan (LLS “Elbrus Agroinvest” farm). The microstructure was investigated using 2½3 cm2 specimens taken between dairy base and the base of the tank throughout the udder fraction along a line passing through the center of the teat canal and lactic sinus in the right front of teat. In the mammary gland of 1/2 Holstein-Swiss crossbred cows the diameter of alveoli were the largest and reached 119 m in the cows of the third lactation, which is 6,2-3,7 % higher compared to peers of other groups (P > 0.999). The smallest diameter of the fat cells are in the black-motley cows (68.3 m) and the largest ones were in Holstein-Swiss crossbred hybrids of the third lactation, the rest of cows take an intermediate position. The greatest increase in the diameter of the fat cells with age was in Holstein ½ black-motley hybrids F2 in which the figure ranges from 68.6 m in heifers to 77.3 m in cows of the third calving. Consequently, according to the development and size of structure elements most important for milk production (the size of the alveoli, and the diameter of the fat globules), the animals improved by Holsteins are superior to the peers of pure Brown Swiss and black-motley cows. It was established that in local Brown Swiss cows the alveoli diameter is higher than that of female-yaks, regardless of their origin, and averages 9.1-11.3 m. By the fat cell diameter, the female-yaks were superior to the Brown Swiss peers by 4.5-5.4 m on average. Thus, mammary glands of Brown Swiss cows and female-yaks imported from Tuva and Kyrgyzstan have characteristics features, namely Brown Swiss cows of local population have larger quantity of glandular epithelial cells, the diameter of alveoli, and the thickness of the main strands, whereas female-yaks have a higher concentration of adipose tissue, a smaller diameter of fat cells and the thickness of interlobular strands. For comparison, we compared the mammary gland in another animal species, the goats of different origin. It was shown that the Zaanen breed has better developed mammary gland with higher biomechanical properties as compared to the local goats’ population.