Influence of fetus weight at birth on the productive traits of first-calf heifers

Abstract

The purpose of the research was to study the infl uence of live weight of calves at birth on indicators of dairy productivity and reproductive ability of fi rst-calf heifers. In order to conduct the experiment 3 groups of fi rst-calf heifers (n=41) of Black-and-White breed were formed depending on the live weight of heifers at birth: the 1th group calves with a live weight of up to 31 kg, 2nd group calves with the live weight from 31 to 36 kg, 3rd group calves with a live weight with of more than 36 kg.It was found as a result of studies that the live weight of heifers at birth with an embryonic development period of more than 280 days signifi cantly exceeded the weight of herdmates with the embryonic development period of 276–280 days by 7,3 % and 275 days or less by 18,8 % (p < 0,01). It was found that the nature of calving and the weight of the fetus at the calving aff ected the further productiv indicators of the fi rst-calf heifers. Thus, 305 days of lactation of cows of the 2nd group signifi cantly exceeded the yield of milk fat of herdmates of the 1st group by 37,1 kg or 26,2 % (p ≤ 0,001), and the yield of milk protein by 33,0 kg or 29,9 % (p ≤ 0,001). At the same time, their superiority over the herdmates of the 3rd group was noted in the yield of milk fat by 6,7 kg or 3,9 % and milk protein by 13,5 kg or 10,4 %. In cows of the 1st group the duration of the open days period was longer by 14 days or 15,0 %, and in the 3rd group by 23 days or 24,7 % (p <0,05) compared with herdmates of the 2nd group. The milk yield for the entire lactation in cows of the 2nd group exceeded the corresponding indicator of herdmates of the 1st group by 260 kg or by 5,7 % (p ≤ 0,01), and the 2nd group by 224 kg or by 4,9 % (p ≤ 0,05). The largest profi t from the conditional sale of products from cows of the 2nd group also provided a high level of profitability in the amount of 36,7 %, which was 22,8 and 27,4 abs.% higher than the corresponding indicators of cows of the 1st and 3rd groups.