The article presents data on the age dynamics of changes in the level of dairy productivity of cows. As a result of the research, the increase in milk yield and the increase amount of milk fat and protein with age of animals was established. The age dependence of qualitative indicators of milk production wasn’t revealed. It was noted that the level of milk productivity of cows in all age periods was higher than the requirements of the first class standard of black-motley breed. An average positive correlation was found between age and milk yield. It was revealed that the productivity of cows is largely determined by their linear affiliation. When analyzing the age-related changes in the reproductive capacity of cows was revealed that the duration of the service period decreases with the age of the animals. When analyzing the age-related changes in the reproductive capacity of cows was revealed that the duration of the service-period decreases with the age of the animals. The duration period between the calves of the average for the cows was optimal, while its reduction with age was observed. It’s noted that as the age of cows increases, the number of inseminations for fertilization increases.
Analysis of the dairy productivity of cows of various origins was made in the APC Kolkhoz Prigorodny. In this farm they breed cattle of black-motley breed. All the cattle stock in the farm are purebred and high-quality, the dairy efficiency of cows is at a fairly high level. In the herd there are cows of five genealogical lines: Vis Back Ideal, R. Sovereign, Mont-week Chieftain, S.T. Rocket, Pubst Governer. As research has shown, cows of the Pubst Governer line were the leaders by milk yield, and the cows of the S.T. Rocket line had the most fat-milk. The cows of the lines Vis Back Ideal and Mont-week Chieftain possessed the highest content of protein mass fraction. As a result of the research it was found out that among the considered population cows were lactated by daughters of 33 bulls. All bulls, whose bioproducts were used in the farm were purebred, had an elite-record class. Proceeding from the possibilities of the farm economy, a tribal nucleus in the dairy herd was identified, and a selection boundary of characteristics was established. Further measures of selection and breeding work with the herd have been developed.
During the day protein mass fraction and fat mass fraction in mares’ milk changes in different ways. The variability of fat content in mare’s milk reaches 60% within 24 hours. Several experiments, including the milking of mares continuously during the day, were conducted to explain the nature of this phenomenon. Differences in the variability of fat and protein contents in the mares’ milk during the day and various way of secretion of the milk components from udder’s secretory cells were explained by the authors in this scientific article. The protein is secreted due to merocrine secretion, and fat secretion mainly occurs due to apocrine secretion. Reduction of fat content in the mares’ milk is caused by the significant increase of milk yield in the early morning, when secretion of synthesized fat slows down. When milk yield is reduced, the secretion of stored fat is increased, which also increases the fat content in milk. It was found that in the morning milk yield of mares is higher than at night by 16.39 %. It was also found that during the day protein mass fraction is higher than it is at night by 5.24 %. The fat content in the mares’ milk during the day is higher than it is at night by 12.24 %. The ratio of daily milk yield and fat content was amounted to 0.22, of daily milk yield and protein mass fraction was + 0.44, and of fat mass fraction and protein mass fraction was + 0.47.
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