Relevance. Lactating cows, especially at the beginning of lactation, consume a higher proportion of minerals received from the diet, and as a rule there is a lack of them. Therefore, the composition of feed mixtures for lactating cows includes premixes, natural mineral additives with a known chemical composition, sapropel, marl, and others that contribute to replenishing the mineral part of the rations.Materials and methods. The objects of research were lactating cows at the third lactation and a recipe for a feed mixture with marl; clay-carbonate rock contains from 50 to 70% CaCO3. Accounting of milk productivity was carried out according to the results of control milkings. The mass fraction of fat and protein in milk was determined on the Clover-1M milk quality analyzer, the calculation of economic efficiency was carried out taking into account the cost of feed and the cost of production and its value.Results. Feeding dairy cows a feed mixture with the addition of marl in the amount of 40 g per day per head contributed to an increase in productivity by 8.2% and a reduction in the cost of energy feed units by 1 kg of milk by 7.7% compared to the control group. The amount of milk fat and protein in milk in the experimental group was increased by 14.5 and 11.7%, respectively. When evaluating the effectiveness of feeding lactating cows feed mixtures with mineral additive in the summer, it turned out that the level of profitability of milk production in the experimental group was greater by 2.77% compared with the control group, which was fed feed mixture without a mineral additive.