The effect of Bisolbi drug based on Bacillus subtilis on the physiological, biochemical and productive parameters of calves was studied. The research and production experiment was carried out in a dairy farm “Kupinskoe” of Samara Region on 30 calves of the Holstein-Frisian breed. The drug increases the intensity of the anabolic processes in animals: the amount of total protein in blood serum of calves of the experimental group at 120 days of age was higher by 8.9% (p≤0.05), albumin 9.2% (p≤0.01), compared with control animals. The purpose of Bisolbi contributed to the increase in the intensity of carbohydrate-lipid metabolism: cholesterol was higher by 23% (p≤0.01), glucose 0.4 mmol/l (p≤0.05) in blood 120-day calves of the experimental group, relative to the data of the control group. It was found that the body weight of calves in the control group at 100 days of age was 105.23±2.11 kg, in the experimental group -108.6±2.19 kg. The average daily gain in the experimental group was significantly higher by 0.075 kg (p≤0.01). At 120 days of age, the body weight of the experimental calves was higher by 4.19 kg (p≤0.05), the average daily increase by 0.080 kg (p≤0.05), relative to the control animals.