The work concerns the study of the reproductive qualities of sows that received, in addition to the main diet, a biologically active preparation (LB-AAP) synthesized from brewer’s yeast waste. For this purpose, two groups of sows were formed, experimental and control ones containing 5 sows in each group. The preparation was administered in addition to the main diet 30 days before farrowing and 10 days after farrowing at 10 ml for each sow. It has been found out that the enrichment of rations for pregnant sows with a biologically active preparation (LB-AAP) allows an increase in the number of born piglets by 0.4 more than in the control group. There were 0.8–0.31 stillborn piglets in the experimental group or 1.0 less compared to the control group. Enrichment of the diets of sows 30 days before farrowing with a biologically active agent had a positive effect on the live weight of the litter at birth and on the 21st day. The average live weight of piglets in the litter of the experimental group was 0.85 kg higher than the average live weight of piglets in the litter of the control group. The average live weight of one piglet at birth in the experimental group was 1.7 kg, and in the control group was 1.4 kg, which is 0.3 kg less. Hematological and biochemical blood tests were studied at the beginning and at the end of the experiment, as well as the amino acid, macro and microelement composition of the preparation.