After calving all subjects of Holstein cows were characterized by an extended period of synthesis and secretion of milk. The animals of the second (control) group had almost one lactation duration – 332 days. Highly productive group III animals were observed with longer lactation period, which was 346 days, that was more than in the same age and second (control) group at 3,91%.

Subjects of second lactation cows were significantly different to each other in terms of milk production for the entire lactation period. So cows of II (control) group produced during lactation at 8051 kg 4% milk, while their peers and groups – 15,2 % less. This dairy animal performance in the third group was the highest and stood at 11625 kg 4% milk. The values were greater than the second (control) group and I, respectively, 30,7 and 47,6 %.

Animals of III group had a high level of milk production, Fat content in milk though inferior to the 0,04 % rate in the control group, but still dominated in absolute terms by 0,03 % of the value of the least productive animals and groups.

Lactating animals had low rate milk protein, cows and second (control) group mass fraction of protein in milk was low and almost identical, and were, respectively, 3,32 and 3,33 %. In the third group of cows it did not exceed 3,26 %. This value is inferior cows index and second (control) group in absolute terms, respectively, 0,06 and 0,07 %.

The most productive Holstein cows Group III were characterized by the highest rates of products like milk fat and protein. Thus, from these animals in lactation period it was obtained at 460 kg milk fat, which was higher than in animals of II (control) groups at 30,5 % and the corresponding value of the animal and the group – 47,8 %. Almost the same difference occured in terms of production and milk protein.

The functional activity of the body of cows for use in industrial technology largely determines the level of implementation of their productive capacity, which was highest in the third group of cows.

The level of performance of Holstein cows second lactation was determined by the ability to high functional activity of lactating body. The highest level of synthesis and secretion of milk marked the third group of animals, the daily milk yield exceeding 45 kg, which was almost 1,7 times higher than in cows of the first group and 24,5 % mentioned analogues of the second (control) group.

Reproductive performance of animals and II (control) groups were close and almost identical, despite the significant difference in productivity. Their insemination index did not exceed two units and averaged 1,9. This figure insemination index provided almost the same length of the service period, the value of which was about 98 days.

Highly productive group III animals demonstrated  the extended service period, the average value of which was about 112 days, which was 11,9 % more than in cows of II (control) group.

Low rate of reproductive ability was inherent for highly productive cows calving second Group III, in which it averaged 0,93, the same at 3,23 % yielded unparalleled value second (control) group.

Thus, in the second lactation cows due to the hormonal stimulation of estrus and ovulation synchronization the inverse relationship performance levels and reproductive function was clearly apparent.

Key words: live weight, average daily milk yield, functional activity , milk fat, milk protein, the service period.