Simple SummaryIn this study, we investigated the immune and antioxidant properties ofLactobacillus johnsoniiRS-7 in weaned pigs. We found that dietary supplementation ofLactobacillus johnsoniiRS-7 can effectively improve growth performance, enhance immune function, and improve the antioxidant performance of weaned pigs. The results of this study provide a feasible nutritional means to solve the weaning stress of piglets effectively.AbstractWe investigated the effects of dietary supplementation of lactic acid bacteria on the immune and antioxidant performance of weaned pigs. A total of 128 Duroc × Landrace × Yorkshire piglets weaned on day 28 with an average body weight of 8.95 ± 1.15 kg were selected and randomly divided into four treatment groups according to body weight and sex for a 28-day study. The four dietary treatments were basal diet (CON), and CON with 0.05% (LJ0.05), 0.1% (LJ0.1), and 0.2% (LJ0.2)Lactobacillus johnsoniiRS-7, respectively. The lowest feed-to-gain ratio (F:G) was found when LJ0.1 was added to the diet. The addition of compound lactic acid bacteria to the diet increased the concentrations of TP, ALB, IgA, and IgM on day 14 and IgG, IgA, and IgM on day 28 (p< 0.05) in the blood, with trait values greater for pigs fed LJ0.1 than CON pigs (p< 0.05). Concentrations of antioxidants (CAT, T-AOC, MDA, T-SOD, and GSH) in serum, intestinal mucosa, spleen, liver, and pancreas improved. In summary, dietary supplementation ofLactobacillus johnsoniiRS-7 improved the antioxidant and immune function of weaned piglets.