Probiotic yeast Saccharomyces cerevisiae coupled with Lactobacillus casei modulates physiological performance and promotes gut microbiota in juvenile barramundi, Lates calcarifer

This study was conducted to investigate the combined effects of probiotic yeast, Saccharomyces cerevisiae, and lactic acid bacteria, Lactobacillus casei on the growth performance, biochemical response, cytokine gene expression, gut histomorphology and microbial composition of juvenile barramundi, Lates calcarifer. Barramundi juveniles with an initial mean weight of 12.17 +/- 0.15 g were randomly allocated into 8 tanks (300L) at a density of 20 fish per tank and fed either a basal diet (control), or the same basal diet supplemented with 1% of S. cerevisiae and 1% of L. casei, collectively termed 'probiotic', for 56 days in quadruplicate. Results indicate that dietary probiotic supplementation produced significant (P < 0.05) improvement in final body weight, specific growth rate and feed conversion ratio compared to the control. A significant increase in serum protein was evident in fish fed the probiotic supplemented diet, while none of the other measured blood and serum parameters were influenced by the probiotic supplementation. Probiotic supplementation also resulted in an upregulation of immune responsive inflammatory cytokine genes (IL-10 and TNF-alpha) and exhibited a higher number of gut mucosal goblet cells and increased microvillous length. The sequence data of the distal gut showed significant positive influence of the probiotic diet on alpha-beta microbial diversities and decreased abundance of pathogenic Staphylococcus and Corynebacterium. These results confirm that the co-supplementation of S. cerevisiae and L. casei improved the growth, immune response and gut health by increasing the diversity of microbiota in juvenile barramundi.