# Assessing the effect of Bacillus rugosus NM007 as a novel probiotic strain on growth performance, hemato-biochemical profile, immune response, digestive enzymes and intestinal histomorphology of Nile tilapia (Oreochromis niloticus)

## TL;DR

This study shows that adding Bacillus rugosus NM007 to fish feed improves growth, health, and digestion in Nile tilapia, making it a promising probiotic for sustainable aquaculture.

## Contribution

The study introduces Bacillus rugosus NM007 as a novel and effective probiotic for Nile tilapia in aquaculture.

## Key findings

- The T2 group showed the highest weight gain and improved hematological values compared to the control.
- Antioxidant activity increased with elevated SOD and CAT levels and reduced MDA in treated groups.
- Histological analysis showed improved intestinal structure and no liver toxicity in probiotic-fed fish.

## Abstract

With the growing global demand for seafood, sustainable aquaculture requires enhancing fish health and feed efficiency while reducing the environmental impact. The current study evaluated the potential probiotics of Bacillus rugosus NM007 in farmed Nile tilapia. Three different doses of B. rugosus NM007 supplemented feed, namely 0.1, 0.2, and 0.3 g/kg, were fed to fish (5.13 ± 0.09 g, N = 240) in triplicate and assigned as T1, T2, and T3, and kept for 90 days. The control group (C) received only the basic commercial diet without supplementation. The treated groups showed significant improvements in growth, feed utilization, and physiological health compared to the control. The T2 group showed the highest growth performance, with a weight gain of 45.66 ± 1.41 per fish (P = 0.001) compared to the control group and superior hematological values, including hemoglobin, RBCs, and WBCs. Liver function improved across all treated groups, with the lowest ALT and AST levels recorded in T2, while T3 showed the highest total protein and albumin levels. Antioxidant activity increased notably, as SOD and CAT were elevated and MDA was reduced in all probiotic-related groups. Lysozyme activity peaked in T2, indicating enhanced immune activity. Digestive enzyme analyses in serum and intestines were significantly higher in all treated groups compared to the control group. Histological analysis revealed improved intestinal villi structure, muscularis thickness, and lymphocyte count, with no signs of liver inflammation or toxicity. Overall, the new B. rugosus NM007 demonstrated strong probiotic potential by enhancing growth, antioxidant defense, immune response, digestive enzyme activity, and tissue health in Nile tilapia, suggesting its promise as a safe and effective novel probiotic for aquaculture.