Influence of the birth season of first-calf heifers on milk productivity and milk production efficiency in the conditions of the Orel region

The purpose of this study was to verify the influence of the season of birth of first-calf heifers of Holstein and Black-and-White breeds on milk productivity and economic efficiency of milk production in the Orel region. The highest milk productivity was demonstrated by Holstein heifers born in the autumn period (from September to November). In terms of the amount of milk fat and milk protein produced in 305 days of lactation, Holstein heifers of autumn exceeded their peers of spring and winter, respectively, by 6.1% (P≤0.01) and 6.6% (P≤0.001) and by 5.4 (P≤0.01) and 5.8% (P≤0.01). First-calf heifers of the black-and-white breed in the autumn months showed a positive trend in terms of milk yield in 305 days of lactation over first-calf heifers of the spring and winter months of birth - by 3.4% and 5.3%. In terms of the amount of milk fat produced in 305 days of lactation, first-calf heifers of the black-and-white breed of autumn exceeded first-calf heifers of the other seasons of birth, respectively: spring - by 6.3% (P≤0.05), summer - by 7.6% (P≤0.05) and winter - by 6.3% (P≤0.05). In terms of the amount of milk protein, first-calf heifers of the autumn birth season had a significant advantage only relating to first-calf heifers of the summer months of birth - by 7.2% (P≤0.05). The calculation showed higher economic efficiency of milk production for 305 days of lactation by first-calf heifers of the Holstein breed born in the autumn months in comparison with first-calf heifers born in the spring - by 14.5 thousand rubles, first-calf heifers born in the summer months - by 2.2 thousand rubles and first-calf heifers born in the winter - by 13.4 thousand rubles. First-calf heifers of the black-and-white breed, born in the autumn months, surpassed the baseline fat content of the first-calf heifers of the spring season of birth by 12.4 thousand rubles in value, the first-calf heifers of the summer season of birth by 14.9 thousand rubles, and the first-calf heifers of the winter season of birth by 13.0 thousand rubles.