This study evaluated the individual and combined effects of L. plantarum and L. reuteri on the growth performance, digestive enzymes, antioxidant, and immunity-related genes in zebrafish. Six hundred zebrafish (38.19±1.4 mg) were randomized into twelve tanks (50 fish per), and fed prepared diets comprising un-supplemented (T0), 1 ×108 CFU/g L. plantarum (T1), 1 ×1011 CFU/kg L. reuteri (T2), and 1 ×108 CFU/g L. plantarum + 1 ×1011 CFU/kg L. reuteri (T3) for 8 weeks. Experimental diets had meaningful effects on weight gain (WG), final weight (FW), and the highest WG and FW were seen in T3. Fish-fed supplemented diets had higher amylase and lipase activities. No significant differences were seen in protease, pepsin, chymotrypsin, and trypsin activities between treatments. The supplemented groups showed a significant increase in lysozyme activity and total immunoglobulin levels. Meaningful differences were noticed in ACH50, lysozyme activity, total immunoglobulin, and IgM levels. ALT levels were markedly higher in T2 and T3. Catalase (CAT), total antioxidant, and glutathione peroxidase (GPX) activity were significantly impacted by the experimental diets. The experimental diets showed no marked impact on superoxide dismutase (SOD) activity, and malondialdehyde (MDA) values. Relative expressions of CAT, GPX, and SOD genes were notably upper in T3. Moreover, IL1, LYZ, and TNFα gene expressions were significantly enhanced in T3 diets. The challenge test with A. hydrophila showed that zebrafish-fed L. plantarum and L. reuteri had a lower mortality rate than the control. Consequently, the combination of L. reuteri and L. plantarum is proposed to improve growth efficiency, immunity, and reduce the negative effects of A. hydrophila infection in zebrafish.
