Aim: This paper presents the results of the studies on "Stimix Zoostim" and "Normosil" probiotics and their influence on fecal microflora, hematologic indicators, immunoresistance, nutrient digestibility, and growth intensity of mother-bonded calves.

Materials and Methods: The calves of the control group were fed with their basic diet (BD) without "Stimix Zoostim" or "Normosil", whereas the calves of the experimental group were fed with their BD supplemented with "Stimix Zoostim" and "Normosil". For 10-20-day-old calves, the daily dose was 10 mL per head, whereas 21-90-day-old calves received 15 mL of probiotics per head per day. The calves of the experimental group were administered probiotics every day. Calves aged 10 to 60 days received probiotics with milk, and then at the age of 61 to 90 days, received probiotics with water. (This is a sequential process. At 60 days old, calf rearing with milk stops, and after that, we use probiotics added to water to rear them). Both groups were administered probiotics twice a day, specifically 50% of the daily dose at each feeding time.

Results: The results in this study proved that "Stimix Zoostim" and "Normosil" probiotics exhibit high probiotic activity and have a positive effect on the calves' fecal microflora. Feeding the calves with probiotics resulted in a significant increase in the number of normal flora, such as lactic acid bacteria and bifidobacteria, and a decrease in the amount of Escherichia. It also resulted in an increase in red blood cells, hemoglobin, and ?-globulins within the physiological range. In our study, we found that the phagocytic reaction in the blood serum of the experimental group was slightly enhanced, suggesting a high response of the body to infectious agents.

Conclusion: Thus, the group of calves receiving probiotic "Stimix Zoostim" exhibited an exceedance of phagocytic activity by 4.8% and the group receiving "Normosil" by 4.4%, in comparison with the control group. The daily dose of 10 mL of probiotics per head for 10-20-day-old calves and 15 mL per head for 21-90-day-old calves also had a positive effect on nutrient digestibility, growth, and forage consumption. The economic benefit per animal was 149.23 and 157.0 rubles, respectively.

Keywords: average gain, blood immunoresistance, forage consumption, hematologic indicators, mother-bonded calves, nutrient digestibility.