Improvements in the growth performance, morphology, gut microbiota, hepatic health, and immune response of juvenile tilapia (Oreochromis niloticus) fed Metschnikowia sp. GXUS03

Abstract

The present study investigated the effects of dietary Metschnikowia sp. GXUS03 on the growth performance, morphology, intestinal flora, hepatic health, and immune response of juvenile tilapia (Oreochromis niloticus). The fish (average weight = 9.67 ± 1.61 g) were administered either a plain basal diet (control check group; CK), a basal diet supplemented with 1 × 107 CFU/g GXUS03 (M01 group), or a basal diet supplemented with 1 × 108 CFU/g GXUS03 (M02 group) for eight weeks. Relative to CK, M01 and M02 had significantly higher final body weights (FBW), weight gain rates (WGR), specific growth rates (SGR), and feed conversion ratios (FCR) (P < 0.05) as well as less hepatic fat vacuolation. M02 also presented significantly upregulated antioxidant enzymes and enhanced antioxidant capacity. After eight weeks, M01 and M02 also exhibited significantly improved autochthonous gut bacterial community and the formation of various potential probiotics. M02 displayed significantly improved survival in response to Streptococcus agalactiae inoculation. This treatment augmented lipid metabolism and the immune response, increased the serum index (complement 3 content and lysozyme activity), and upregulated hepatic Toll-like receptor (TLR2, MyD88), lipoprotein lipase (LPL), and immune-related (C3, lyz) genes. The foregoing results indicate that 1 × 108 CFU/g Metschnikowia sp. GXUS03 dietary supplementation improved the growth performance indices, liver health, and immune responses in tilapia.