The advancement of dairy farming hinges significantly on establishing a robust forage foundation alongside employing breeds of cattle with high productivity. In autumn 2013, 150 Red Steppe heifers were transferred from Altai Territory to OOO Byan in Ust-Aldan District. This breed is recognized for its substantial genetic capacity for milk production; under optimal management, yields range from 3,000 to 6,000 kg per lactation. Yakutia’s harsh climatic contrast—with severe winters, notably low temperatures, and brief summers—poses challenges for producing adequate high-quality fodder compared to Altai. In 2015, a study was executed on first-calf Red Steppe heifers, comparing dietary impacts on milk output. The experimental group's diet incorporated 5.0 kg of mixed grass hay, 4.3 kg of seeded cereal hay, 15.0 kg of fresh oats, 2.0 kg of dried brewer's grains, and 2.0 kg of local feed enhanced with 300 g of Felutsen daily, totaling 118.0 MJ of metabolizable energy and 14.4 kg of total dry matter. The control group’s feed lacked the brewer's grains and Felutsen supplement. Results demonstrated a superior milk yield by 18.9% in the experimental group. Highlighting the diet’s effectiveness, the inclusion of 13% dried brewer's grains and 17% Felutsen-fortified feed proved financially beneficial, generating an additional income of 52,138.0 rubles with a 10.0% profit margin in milk production. This study aimed to evaluate the implications of enriching cattle diets with energy-protein-mineral supplements on the lactational performance of first-calf heifers under northern environmental conditions.