Microbial, immune and antioxidant responses of Nile tilapia with dietary nano-curcumin supplements under chronic low temperatures

A 56-day feeding period was performed to investigate the possible impacts of dietary nano curcumin (0, 50, 100, 150, and 200 ppm) on the growth, nutrient utilization, non-specific immune parameters, antioxidants in Nile tilapia under chronic low temperature (21.02 ± 0.11 °C). Fishes (n = 225; Initial weight = 4.39 ± 0.08 g/fish) were randomly stocked at 15 fish/tank for five experimental groups in triplicates. Under low-temperature circumstances, dietary curcumin in nano form showed no notable alteration in growth variable, nutrient efficiency, digestive enzymes efficiency, biometric indices, survival rates, and hematological components. Meanwhile, the serum of fishes with nano curcumin diets under low-temperature stress displayed higher total protein as well as lower glucose, cortisol, and total cholesterol compared with the control group. Moreover, fish fed nano curcumin diets displayed higher lysozyme and bactericidal activities compared to the control group and the best performance was found at dietary nano curcumin level of ≥100 ppm. Also, groups fed the basal diet demonstrated the poorest antioxidant capacity, and the best superoxide dismutase (SOD) and glutathione peroxidase (GPx) existed in fish with nano curcumin diets while the best catalase (CAT) efficiency occurred at higher nano curcumin levels ≥100 ppm. In addition, higher counts of intestinal microbiota in terms of total bacterial count (TBC), total yeast and molds count (TYMC), and coliform were noticed in fish consumed the basal diet compared to groups fed on nano curcumin diets. In conclusion, incorporating nano curcumin at a level of ≥100 mg/kg diet (particularly at 150 mg/kg) improved a non-specific immune response, antioxidant, and healthier gastrointestinal microbiota in Nile tilapia under chronic low-temperature stress.