Dependence of milk productivity Holstein cows on the duration of lactation period and organism's physiological activity

Characterizing the productive qualities of Holstein cows, it is necessary to note a clear increase in milk yield of cows from the first to the fourth lactation, and already at the fifth lactation there is a slight decrease in milk productivity. Thus, cows of the third lactation were no longer characterized by milk yields of up to 9,000 kg of milk. At the same time, animals of the fourth and fifth lactations also had no milk productivity of up to 9,000 kg, but no more than 10,000 kg in 305 days of lactation were the same. In the conducted studies, the duration of the lactation period in different cows significantly deviated from the normative indicator, which is 305 days, ie 10 months. Thus, even with the stimulation of ovulation on the ovaries of cows, the duration of lactation exceeds the normative parameters. Particularly long lactation period in maladapted first-borns, which exceeds the norm by 42.9%. However, with the age of the cows, the lactation period, although exceeding the norm, is still noticeable a slight reduction. It is established that the increase in milk productivity of cows occurs from the first to the fourth lactation, and already at the fifth lactation there is a slight decrease in it, indicating some physiological exhaustion of the body. Indicators of the ratio of the magnitude of the milk to their live weight also testify to this. Thus, Holstein animals of the fourth and fifth lactations show the highest rates of both milk productivity for 305 days and physiological activity of the organism. During this period, per kilogram of live weight of cows accounted for 15.0 and 16.0 kg of secreted milk, respectively, whereas in animals of the first and second lactations this figure was lower by 14.3 and 11.8%, respectively. Animals I and III (control) groups, respectively, in the first and third lactations, respectively, of 0.5 kg of milk fat and 0.4 kg of milk protein per unit body weight had the closest and lowest values of milk fat and protein indices. These values were inferior to those of group II, IV and V cows, respectively, in the second, fourth and fifth, which in turn secreted 0.6 kg of milk fat and 0.5 kg of milk protein per kilogram of live weight. The realization of genetic potential by Holstein cows is not stably programmed because it depends on the individual response to the operating conditions. The physiological depletion of the body through intensive technology indicates that the level of dairy productivity in cows from the first to the fourth calving increases, and then decreases slightly.