Dietary Chitosan Nanoparticles Enhance Growth, Antioxidant Defenses, Immunity, and Aeromonas veronii biovar sobria Resistance in Nile tilapia Oreochromis niloticus

While chitosan is widely used in aquaculture feed, chitosan nanoparticles (CNPs) offer potential advantages due to their enhanced absorption. This study investigated the safe use of CNP levels in Nile tilapia feed, evaluating its impact on growth, immunity, and disease resistance. Five experimental diets were formulated and supplemented with zero chitosan (served as a control group), 1g/kg of chitosan (CS), and 1, 3, and 5 g/kg of CNPs. Each diet was randomly assigned to three replicate groups of 45 fish per group (15 fish/tank) with an average weight of (42.10 ± 0.05g, mean ± S.E.) twice daily (09:00 a.m. and 4:00 p.m.) to apparent satiation for two months. At the end of the feeding trial, fish fed 5 g/ kg of CNPs had the highest growth performance. However, no significant variations (p > 0.05) in somatic index were seen between the experimental groups. All chitosan and CNP-enriched groups exhibited improved intestinal morphology compared to the control group, characterized by increased villus length and width, reduced necrosis of intestinal tips, and better overall tissue integrity, with the CNP 3g and 5g groups demonstrating the most favorable intestinal structure. The CNP-treated groups (3, 5 g/kg) had significantly higher blood indices and serum globulin. Malondialdehyde (MDA) levels were lower in the CNP-treated groups compared to the chitosan macromolecule group. There was a substantial rise in glutathione (GSH), total antioxidant capacity (TAC), phagocytic index, and respiratory burst activity in the 5 g/kg CNP-treated group. The dietary addition of 5 g/kg of CNPs raised mRNA expression for TLR-2, MUC-2, and IGF-1, but there was no significant difference in HSP70 expression across treatments. After the experimental challenge with Aeromonas veronii biovar sobria, the groups that received 3 and 5 g/kg of CNPs exhibited the lowest mortality rates. Overall, the results suggest that including 5g/kg of CNPs in fish food is safe and effective for enhancing their health and growth, making it a promising addition to aquaculture feed.