The physiological status of dairy cows has been studied. By cows within 120 days after calving, were fed the feed additive «Ketostop-El», 300 g per head, in addition to the ration. The clinical status of healthy animals did not change after the supplement was used. However, clinical improvement was recorded in two cows with symptoms of bursitis and gastrointestinal dysfunction. The inclusion of the supplement in the diet of cows contributed to an increase in the concentration of hemoglobin in the blood, hematocrit and the concentration of hemoglobin in the erythrocyte to physiological values. The number of basophils and eosinophils in the blood of animals increased by an average of 2.3 and 3.6 times compared to their level before the addition to the ration. The level of all metabolites of the blood serum of dairy cows, except for the concentration of triglycerides, corresponded to the average values. It should be noted that the concentration of creatinine in the blood serum decreased by an average of 1.5 times, glucose - by 26 %, total calcium - by 16 %, the ratio of calcium and phosphorus - by 44 %, reserve alkalinity - by 26 %. LT activity decreased by 19 %, AST - by 1.7 times. At the same time, the content of inorganic phosphorus increased by an average of 48 % compared to their amount before the supplement was included in the diet, and at the same time did not go beyond the reference values. At the same time, the use of «Ketostop-El» contributed to a decrease in urine pH to 7.7 ± 0.1, protein content - to 0.35 ± 0.05 g / l, ketones - to 0.35 ± 0.02 mmol / l. The proposed dose of the feed additive «Ketostop-El» (300 g per head) to increase milk productivity, prevents food stress, exerting a positive effect on the body of animals, and makes it easier to adapt to the conditions of the farm.