Abstract
Dietary coenzyme Q10 (CoQ10) and vitamin C (Vc) are natural immunostimulants and antioxidants involved in improving the performances and health conditions of aquatic animals. In this context, six diets were formulated and supplemented with CoQ10 and Vc at 0/0 (D1), 0/400 (D2), 0/600 (D3), 20/0 (D4), 20/400 (D5) and 20/600 (D6) mg of CoQ10/Vc per kg diet and fed to Nile tilapia for 56 days. The obtained results displayed higher weight gain, specific growth rate, and feed efficiency ratio in all groups than the control group (D1). Concurrently, feed intake, amylase, lipase, and protease activities were significantly higher in D5 and D6 groups than the other groups (P < 0.05). Conversely, the whole-body crude lipid content was markedly decreased with dietary CoQ10 or/and Vc, and the highest value was in fish fed D1 (P < 0.05). Interestingly, fish fed on D5 and D6 diets exhibited the lowest glucose, cortisol, total cholesterol, triglycerides, and the highest total protein among the other groups (P < 0.05). The lowest activities of serum and mucus lysozyme and bactericidal were found in fish groups fed D1, and the highest values were in groups fed D5 and D6 diets (P < 0.05). In the same line, the antioxidant capacity (superoxide dismutase and catalase) and the related genes (SOD and CAT) displayed the highest values in the group of fish fed on D5 and D6 diets, while the lowest values were in fish fed D1 (P < 0.05). Correspondingly, on the day 14th post-challenge, the relative percentage of survival rate (RPS) of tilapia injected with Streptococcus agalactiae recorded significantly higher RSP values in D2, D3, D4, D5, and D6 groups than the control (D1) group (P < 0.05). In conclusion, dietary CoQ10 and Vc had significant interaction influence on growth performance, feed efficiency, digestive enzyme activity, biochemical blood indices, immune response, and antioxidative capacity. More specifically, the enhanced performances of Nile tilapia by CoQ10 and VC supplements increased their resistance against S. agalactiae infection.