The aim of this study is to assess the effect of the Bacillus rugosus strain as a probiotic on growth performance, hemato-biochemical profile, intestinal morphometry, immune response, digestive enzymes and antioxidant activity of Nile tilapia. Three different doses 0 g/kg, 0.1g/kg, 0.2g/kg of B. rugosus potential probiotic powder have been supplemented to fish (5.13±0.09g, N=240) and representing the triplicate control (C), T1 and T2 groups and kept for 90 days.
The probiotic-supplemented groups demonstrated improved performance and health status. The treatment groups (T1, T2, and T3) outperformed the control group in terms of fish growth. Specifically, the T2 group showed the highest results. The blood analysis showed significant differences between B. rugosus supplemented groups and the control group, especially in T2, which has the highest levels for hemoglobin, red blood cells and white blood cells. Biochemical assessments revealed significant improvements in liver enzyme activities in probiotic related group with the lowest ALT and AST recorded in T2 groups. The total protein and albumin levels were the highest in T3. Oxidative stress markers indicated a significant difference in probiotic related groups that the highest levels of SOD and CAT were recorded in T3 group. T3 also showed the lowest MDA levels. Lysozyme activity showed the highest level in T2 group, and levels of immunoglobulin G (IgG) were also increased in probiotic related groups. Digestive enzymes amylase and lipase also have a significant difference in probiotic related groups when compared to the control group. In addition, B. rugosus potential probiotic also reveals an improvement in the intestinal histological and morphometric parameters as compared to control group. The muscularis thickness, villi height, villi width and number of lymphocytes analysis results showed significant effects. The liver histological analysis showed that the probiotic related groups have no harmful effect in fish, as there was absence for signs of hepatotoxicity. After 90-days experimental trial the histological examination of liver tissues did not show any inflammation changing, necrosis or pathological lesion.
Based on these findings, B. rugosus potential probiotic shown promising results in enhancing the health and performance of Nile tilapia and could serve as a novel probiotic for aquaculture.