The article presents the development dynamics of Simmental replacement heifers. The maximum indicators of individuals were achieved at the age of 5 to 10 months with the average daily weight gain between 1118 and 1513 g. The dependence between the first insemination age and milk production was examined. The highest milk yield, considering three lactations, was observed in first-calf heifers that calved at the age of 27–28 and 29–30 months. The milk yield for the first lactation was 6630 and 6567 kg and for the highest lactation – 7704 and 7722 kg milk, respectively. In most cases, heifers were successfully inseminated at the age of 16 to 18 months. The important condition was that the heifer’s body weight reached 65 to 70 % of the adult animal’s weight during this period. Forming a dairy herd of cows, the specialists should initially select, raise, and milk first-calf heifers in the direction of the intended milk productivity.
Popova et al. (Wed,) studied this question.