Relevance. The milk production of cows and their productive longevity is determined by many genetic and paratypical factors, one of which is the duration of the service period. The relationship between milk productivity and the reproductive capacity of cows is largely due to the predominance of the proportion of concentrates in the rations. With an increase in milk production in a herd, the number of cows with diseases of the reproductive organs increases and the number of abortions in the first months of pregnancy increases [1, 10, 14].

It is known that the reproductive ability of cows as a complex morphological system is a function formed in the process of evolution, in which all the traits are closely related. They directly affect the efficiency of selection in the herd, and the service period, in turn, affects reproduction and milk productivity [2, 5, 13]. Therefore, the service period is one of the components of the cow’s physiological cycle, during which it must be prepared for fruitful insemination. The duration of this period as a production indicator gives a general idea of the reproductive qualities of both the herd as a whole and each animal in particular [4, 6, 8].

To increase milk production, it is possible to lengthen the service period to obtain a longer lactation. However, the study of this issue shows that in this case the dry period is also lengthened, and the average daily milk yield as a whole per lactation decreases. There is no consensus among experts on the duration of the service period. The classical definition indicates that the duration of the service period should be equal to 80 days since, with this duration, milk production is most efficient. According to most authors, it is necessary to take into account the yield of calves, the level of milk production, the duration of practical use [3, 7, 9].

The purpose of the research is to determine the level of milk production and reproductive capacity of cows depending on the duration of the service period.