The aim of the study was to evaluate the effect of moderate-early mating on the performance and reproductive functions of cows later in life weight and age at insemination. Four groups of heifers were selected for the experiment, taking into account their age and live weight at the time of insemination. The results of the study showed that age and live weight of heifers at the time of first insemination influenced milk productivity. The difference for 100 days of lactation between 1 and 2 groups averaged 49 liters of milk per head, between 3 and 4 groups - 62 liters of milk. Higher fat-milk yield is observed in animals with higher live weight (groups 2 and 4). The difference in 1 and 2 groups was 1.94%, and in 3 and 4 groups - 0.55%. It was found that calves from heifers with higher live weight at the first mating were born larger. The difference in live weight at the end of the period between groups 1 and 2 of calves was 9.4 kilograms, and between groups 3 and 4 - 9.6 kilograms. During the study period, postpartum complications and diseases were practically not observed in first calves of groups 2 and 4: 1 case was observed in group 2, and 2 cases of diseases were observed in group 4. Also, the duration of service period in them was normal and amounted to 66 days in group 2 and 63 days in group 4. In contrast, 7 cases of postpartum retention (3 cases in group 1 and 4 cases in group 3) and a longer service period were observed among animals of groups 1 and 3. The obtained data may have important practical value for optimization of calving process and increase of milk productivity of cows.
first heifers, live weight, age, insemination, productive indices
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