Dairy productivity of mixed-aged Holstein cows with prolonged lactation function

Presented study results of the productivity of mixed-aged cows with prolonged lactation. The formation of experimental groups was carried out according to the principle of analog groups, taking into account breed, live weight, age and physiological condition (lactation):25 animals in groups I, II, III and IV and 10 animals in group V. It was found that with the industrial technology of Holstein cows exploitation, regardless of their age, the duration of the lactation period was almost twice as long as the scientifically substantiated value and ranges from 561.2 to 610.9 days. At the same time, the milk productivity level of the cows in I and IV groups slightly exceeded 13 000 kg of milk per lactation, while in cows if II, III (control), and V groups – this value was higher than 15 000 kg. With prolonged lactation, the milk yield in the experimental groups of animals in terms of 305 days was kept at a fairly high level and there was a definite tendency to an increase in milk yield depending on the age of the animals. The first-calf heifers of group I were characterized by a relatively low milk yield since they gave only 13 291.8 kg of milk for the entire lactation, and in terms of 305 days – 7 944.1 kg, which was 13.57% and compared to III (control) group was 19.54% lower (P < 0.01). Animals of the fifth lactation from group V had the highest milk yield, in which the milk yield per lactation and per 305 days amounted to 15 818.5 kg and 9 716.7 kg of milk, respectively. With intensive exploitation technology and with the increasing age of Holstein cows, complete adaptation occurs, as a result of which their genetic potential for milk production is realized at a high level. This was indicated by the milk yield dynamics in experimental animals of different ages, in which, under the same conditions of feeding and housing, they were gradually increased from the first to the fifth lactation.