This study aimed to verify the possible positive effects of feeding the commercial probiotic Bioplus 2BC® [Bacillus subtilis (1.6 × 1010 CFU/g) and Bacillus licheniformis (1.6 × 1010 CFU/g)] to Nile tilapia on its growth performance, nutrient digestibility, gut microbiology, haematology (hematimetric index, erythrocyte, leucocyte and thrombocyte counts) and innate immunology (lysozyme, burst respiratory and phagocyte activities). For this purpose, one in vivo assay was performed following a completely randomized design, with four treatments (0.00%; 0.02%; 0.04%; and 0.08% of probiotic inclusion on ratio) and four replicates. The fish fed with diets containing 0.04% and 0.08% of probiotics presented higher weight gain than the control group, as well as higher thrombocyte counts in the bloodstream. The positive effect of the probiotics on the gut microbiota was illustrated by the higher richness and habitability indexes, soaring genetic variability. On the contrary of control, the groups fed with probiotic had Firmicutes, Fusobacteria and Bacteroidetes phyla, and a lower percentage of Proteobacteria. The inclusion of 0.04% and 0.08% of B. subtilis and B. licherniformis in the fed provides better growth performance and modifies the intestinal microbiota, reducing the class of potential pathogen agent species. The establishment of a beneficial microorganism population may improve host health.

The aim of this research was to evaluate the possible positive effects of feeding Nile tilapia (Oreochromis niloticus) with a diet containing a commercial probiotic AQUA-PHOTO ® [Lactobacillus plantarum (1.51 × 10 6 CFU g −1 ) and Bacillus subtilis (1.34 × 10 7 CFU g −1 )] on digestive enzymes' activity and gut microbiome profile. The experimental design was completely randomized, with two treatments [control and probiotic diets (0.08 g.100 g −1 of feed)] and six replicate tanks per group (n = 8 animals per experimental unit, mean weight 8.18 g ± 1.85 g). The 96 fish were distributed into 12 aquaria and fed with the probiotic and control diets for 7 days. After this period, intestine samples (anterior, middle, and posterior portions) were collected from two individuals per tank. The samples were analyzed for assessment of DGGE profile and digestive enzymes' activity (amylase, alkaline protease, and alkaline phosphatase). The results were subjected to analysis of variance (ANOVA) and the means compared by t test (P < 0.05). The addition of B. subtilis and L. plantarum in the diets modulated the intestinal microbial biodiversity, more specifically the species richness and habitability index (P < 0.05). Besides, probiotic feeding also increased specific amylase activity in the anterior gut (P < 0.05). The other variables studied did not show any significant differences between treatments. The oral administration of B. subtilis and L. plantarum (AQUA-PHOTO ® ) modulates intestinal microbiota profile and increases the amylase enzymatic activity. Therefore, this measure may provide better utilization of carbohydrate sources in the diet, supplying energy for Nile tilapia growth.

The aim of this study was to evaluate the effects of a probiotic, composed of Bacillus subtilis and Lactobacillus plantarum in Nile tilapia fry during the sex reversal phase under stress conditions caused by high stocking density. This experiment was conducted in the Fisheries Institute of São Paulo. The experiment design was completely randomized with four treatments: 1) probiotic added feed, 2) probiotic added to water, 3) probiotic added to feed and water and 4) control diet; with three replicates. The variables analyzed were: final weight, total length, specific growth rate, survival, intestinal microbiology and gene expression of TNF-α and HSP-70. The results of the zootechnical performance of growth and gene expression did not show significant differences between treatments in the parameters evaluated (P>0.05). In the intestinal tract of fry raised in water with added probiotic, log10 CFU (7.72 ± 0.51) count of Bacillus spp. was higher than with other treatments which themselves did not differ significantly. It was concluded that the addition of a probiotic of Bacillus subtilis and Lactobacillus plantarum in the feed or water of Nile tilapia fry during the sex reversal phase did not affect the zootechnical performance of growth or expression the genes studied, but modified the intestinal microbiota.