The lactation curve is determined by the level of milk productivity and individual characteristics of feeding and housing. The authors have researched the study of milk productivity of Yaroslavskaya breed cows and the influence of lactational activity in the conditions of Agricultural Production Cooperative ART of the PravoberezhnyDistrict of the Republic of North Ossetia -Alania in 2019-2020.The farm is located at 43°12 ' 37 "north latitude 44°29'53" east longitude. When breeding "Yaroslavka",

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... methods of selection and selection of animals were used without the use of foreign breeds, so that the Yaroslavl breed represents a separate population. Its allelofond differs significantly from that of other dairy breeds of cattle. Fifty-six first-calf cows were studied. When evaluating milk productivity, the following indicators were taken into account: milk yield for 90 and 305 days of lactation, fat and protein content, milk fat and protein, the highest daily milk yield, lactation fullness index, and lactation stability ratio. It was found that for the studied cows, the peak of lactation fell on the third month; the maximum milk yield was 434.8, 566.9, and 746.9 kg, respectively, for the groups. The increase in milk yield for the first month was higher in the first group, with milk yields up to 3,000 kg -22.0%, in the second and third groups -13% and 17.9%, respectively. In the studied first-calf cows, the lactation constancy ratio was 91.1, 82.6, and 87.3%, respectively, for the groups. The first-calf cows with the highest stable lactation curve had a higher lactation fullness ratio -93.6%. It should also be noted that cows with a lactation constancy ratio of more than 93.6% (2,109.0 and 4,882.3 kg) had high milk yields for the first 90 days and 305 days of lactation.