Experiments were performed to evaluate the effect of the biological preparation "BioBact" Microclimate" based on Bacillus subtilis D18 on the microflora of indoor livestock farm sections. Experimental treatment of farrowing sections was carried out at one of the livestock farms in Tomsk region, West Siberia. Monitoring of the sanitary-indicative microorganisms counts revealed a decrease in the total aerobic microbial counts, number of E. coli group bacteria, enteric bacteria and Staphylococcus spp. in the experimental sections of the livestock farm compared to control conditions.