Milk productivity and reproductive ability of Holstein heifers depending on live weight at first insemination

The purpose of the research is to substantiate the age and live weight of Holstein heifers at the first artificial insemination. Experimental studies were conducted on inseminated heifers at the age of 13 months with different live weight, from which 3 groups of animals of 10 heads each were formed, taking into account live weight. The first group of animals with a live weight at the first insemination of 360 kg, the 2nd group – 380 kg, the 3rd group – 400 kg. Using the methods of timing and visual observation, the following indicators were studied in the studied groups of heifers: pregnancy, the course of childbirth and the postpartum period, restoration of reproductive function after calving, milk productivity and milk quality indicators. Based on the conducted studies, it was found that the live weight of heifers and age at the first insemination have a significant impact on their reproductive ability, as well as on the reproductive function of the first heifers and, subsequently, on the level of milk productivity and milk quality indicators. The optimal live weight during the first insemination of Holstein heifers is a live weight of 380 kg, which provides an increase in fertilization by 10%, reduces the age of the first calving, the period of fruitful insemination by 3-7 days, increases the level of milk productivity by 2.3% and does not reduce the quality of milk.