Effects of melatonin on growth, antioxidation and non-specific immunity of Oncorhynchus masou

The aim of this study was to investigate the effects of melatonin on the growth, antioxidation and non-specific immunity of Oncorhynchus masou. The experiment randomly divided 450 healthy O.masou with similar initial weights into 5 groups, with 3 replicates in each group and 30 fish in each replicate. Feed different concentrations of melatonin (0, 30, 60, 90 and 120 mg/kg) separately for a trial period of 56 days. The results showed that ① Compared with the control group, the addition of 60, 90 and 120 mg/kg melatonin to the feed significantly increased the average weight gain rate, specific growth rate, and feed efficiency of O.masou; the addition of melatonin at doses of 30, 60, 90 and 120 mg/kg to the feed significantly increased the fat percentage; and feed efficiency of the group with 90 mg/kg melatonin added to the feed were significantly higher than those of the other groups. ② Compared with the control group, adding 30, 60, 90 and 120 mg/kg melatonin to the feed significantly increased the activities of Total Antioxidant Capacity(T-AOC), Total Superoxide Dismutase(T-SOD), and Glutathione(GSH) in serum, as well as T-AOC, T-SOD, and Glutathione Peroxidase(GSH-Px) in liver. The levels of Catalase(CAT), GSH-Px in serum and GSH, CAT in liver were significantly higher in the 60and 120 mg/kg melatonin groups than in other groups; adding 30, 60, 90 and 120 mg/kg melatonin to the feed significantly reduced the Malondialdehyde(MDA) content in the serum and liver of O.masou; the activities of T-AOC, T-SOD, GSH, CAT, and GSH-Px were highest in the 90 mg/kg melatonin group, significantly higher than those in other groups; the MDA content in the 90 mg/kg melatonin group was the lowest, significantly lower than other groups.③ Compared with the control group, the addition of 30, 60, 90 and 120 mg/kg melatonin to the feed significantly increased the levels of serum Complement Component 4(C4), Complement Component 3(C3), Immunoglobulin M(IgM), Lysozyme(LZM), and Alkaline Phosphatase(AKP) in the liver of O.masou; Adding 60, 90 mg/kg, and 120 mg/kg melatonin to the feed significantly increased the levels of C3, LZM, IgM and AKP in the serum and C4 in the liver of O.masou; The serum and liver C3, C4, IgM, LZM and AKP levels were highest in the 90 mg/kg melatonin treatment group, significantly higher than those in other groups .Under this test condition, when the level of melatonin in feed is 90-120 mg/kg, it can effectively improve the growth performance, antioxidant capacity and non-specific immunity of O.masou; to achieve the maximum weight gain rate of Oncorhynchus masou, the recommended amount of melatonin added to the feed is 91.98 mg/kg. The above results indicate that adding melatonin at different levels as a feed additive for O.masou can improve its growth performance by increasing its average weight gain rate, specific growth rate, feed efficiency, and fatness.