Abstract
A comparative analysis of the antibacterial activity of authentic strains of lactobacilli was conducted. Primary data on the antibacterial activity of Lactobacillus acidophilus, L. brevis, and L. plantarum were obtained, as well as the impact of L. brevis in the composition of the extruded feed «BioMar» on the physiological condition of juvenile rainbow trout. The supplement was orally introduced into the main diet at a concentration of 2×108 cells of L. brevis per milligram of feed for 30 days. The obtained results were evaluated based on changes in the growth indicators, survival rates, and the diversity of the background microflora in the intestinal contents of trout fry in the experimental and control groups. According to the experiment results, the physiological indicators of trout fry receiving the premix with lactobacilli in the feed were higher than those in the control group. In the intestinal contents of the experimental group, a high proportion of lactobacilli (9.4%) was maintained, unlike the control group, which was on a diet without any additives (average values of lactobacilli in the intestinal contents did not exceed 0.6%). The studied biological properties of the Lactobacillus brevis strain make it a potential probiotic culture for use in therapeutic and prophylactic feed formulations for aquaculture.