Nano-chitosan encapsulation of bee venom: a potential therapeutic strategy for enhancing tilapia health and resistance to Aeromonas hydrophila

Abstract Nanotechnology-driven innovations in feed additives hold significant potential to transform aquatic animal nutrition by enabling unprecedented levels of efficiency, precision, and environmental responsibility. This study investigates the effects of dietary nano-chitosan loaded with bee venom (BV-CSNPs) on growth performance, physiological responses, antioxidant and immune-related gene expression, and susceptibility to Aeromonas hydrophila challenge in red tilapia ( Oreochromis niloticus × O. mossambicus ). In a 70-day feeding trial, 1200 red tilapia were randomly assigned to four dietary treatments ( n = 300 per group): a basal diet (control) and three diets supplemented with BV-CSNPs at concentrations of 0.1, 0.2, and 0.3 mg/kg. Fish fed the BV-CSNPs-supplemented diets showed significantly enhanced growth indices and improved body composition compared to the control group ( P < 0.05). Furthermore, dietary inclusion of BV-CSNPs resulted in decreased levels of total cholesterol and triglycerides, as well as reduced liver enzyme activity (AST, ALT, and ALP), concurrent with an increase in blood protein levels. Dietary supplementation with BV-CSNPs significantly enhanced immune parameters, including phagocytic and lysozyme activities, and serum IgM levels, as well as antioxidant enzyme activities (CAT, GPx, and SOD) ( P < 0.05). Notably, the activity levels of digestive enzymes (protease, amylase, and lipase) were significantly elevated across all BV-CSNPs treatment groups, with the most pronounced improvements observed in the 0.3 mg/kg BV-CSNPs group ( P < 0.05). Dietary supplementation with BV-CSNPs improved intestinal layer morphology and modulated the gut microbiota by promoting a reduction in potentially pathogenic bacteria and an increase in beneficial bacteria. Furthermore, fish fed diets supplemented with BV-CSNPs exhibited significant upregulation of genes associated with growth ( GH , IGF1-R , and IGF-1 ), immunity ( IL-8 , IL-1β ), and antioxidant defense ( SOD , CAT , GPx ) compared to the control group. Similarly, dietary administration of BV-CSNPs notably reduced mortality rates following A. hydrophila challenge. In conclusion, dietary supplementation with BV-CSNPs elicited a multifaceted improvement in growth performance and overall health of red tilapia by modulating intestinal health, immunological function, antioxidant capacity, and digestive enzyme activity. These findings suggest that BV-CSNPs effectively enhance overall fish health and confer protection against A. hydrophila challenge.