This paper aims to monitor the impact of Lactobacillus sporogenes (LS), Saccharomyces cerevisiae (SC), the combination thereof Lactobacillus sporogenes and Saccharomyces cerevisiae (CLS) on the health status and the live weight gain in calves compared to a control group (C). The experiment took place in the period from March 2022 to March 2023. 100 Holstein heifers in the age from 1 to 56 days were included in the experiment. The differences in live weight gain were significant when the live weight gains were compared in the first 14 days after birth between the CLS vs C group (63,36.72 ± 4.81 vs 59.55 ± 4.55, P < 0,05) and in 56 days after the birth between the CLS vs C group, LS vs C group and SC vs C group (87,34 ± 4.95 kg vs 83.15 ± 5.32 kg, P < 0,01; 86.41 ± 5.34 kg vs 83.15 ± 5.32 kg, P < 0.05 an 85.92 ± 5.86 kg vs 83.15 ± 5.32 kg, P < 0.05). The differences in live weight gain between the experimental groups were not proved statistically P > 0.05. The impact on decrease and duration of diarrhea was not proved statistically P = 0.0634. However, a tendency to decrease the occurrence and duration thereof was proved. The impact of feed additives on the transmission of passive immunity in calves in their first week of life was not proved as statistically significant. © 2023, University of Zagreb – Faculty of Agriculture. All rights reserved.