Effects of Saccharomyces cerevisiae Postbiotic on Growth Performance, Selected Immune and Antioxidant Gene Expression, and Resistance to Fusarium oxysporum Infection in Nile Tilapia (Oreochromis niloticus).

This study evaluated graded dietary doses of Saccharomyces cerevisiae postbiotic (0, 1.25, 2.5 and 5 g kg-1) on growth, feed utilization, serum biochemistry, expression of IGF-1, SOD2, IL-1β, IL-10 and IgM, and resistance to Fusarium oxysporum in Nile tilapia (Oreochromis niloticus; 35.1 ± 0.9 g) after 30 and 60 days of feeding. Although the 5 g Kg-1 inclusion significantly increased WG (59.4 ± 0.9) and SGR (1.5 ± 0.0) and decreased FCR (0.8 ± 0.0), significant positive effects on multiple endpoints were also recorded at 1.25 and 2.5 g/kg. Serum total protein and globulin rose with increasing dose and feeding duration, while albumin showed limited change, lowering the A/G ratio. AST remained unchanged. Creatinine and glucose declined with postbiotic supplementation; the glucose reduction effect was dose-dependent, whereas creatinine was unaffected by feeding duration. The highest gene expression of hepatic IGF-1, SOD2, IL-1β, and IL-10 and splenic IL-1β, IL-10, and IgM was in T3 at both checkpoints; however, the highest gene expression of intestinal IL-1β, IL-10, and IgM expression was in T1 at both time points. The pathogenicity experiment showed a significant survival against F. oxysporum (p < 0.0001) compared to controls. The results suggested that dietary S. cerevisiae postbiotic improved growth, biochemical and molecular responses, and survival of Nile tilapia against F. oxysporum.