Abstract
A 50-day feeding trial was conducted to evaluate the effects of five different levels of low molecular weight chitooligosaccharides (LMW-COS) (0, 0.1, 0.2, 0.4, and 0.8 g kg(-1)) on growth performance, serum parameters, body composition, and non-specific immunity in Nile tilapia (Oreochromis niloticus). A total of 600 fish were divided into 5 treatments with 4 replicates of 30 fish per tank. The results showed that dietary supplementation with 0.4 or 0.8 g kg(-1) COS significantly improved the final body weight, specific growth rate, feed efficiency rate, and protein efficiency ratio of fish (P < 0.05). The supplementation of COS did not significantly affect the content of blood albumin, globin, and glucose, but the trend of enhancing blood total protein and lowering cholesterol and triglyceride was observed with the gradient levels of COS. Immune responses assay showed that dietary supplementation with 0.4 or 0.8 g kg(-1) COS significantly improved the phagocytic activity, serum bactericidal activity, and lysozyme activity in tilapia (P < 0.05); there were no significant differences between 0.4 and 0.8 g kg(-1) of COS (P > 0.05). In one word, the supplementation of 0.4 and 0.8 g kg(-1) COS significantly increased the growth performance and non-specific immunity of Nile tilapia; the recommended COS supplementation in diet is 0.4 g kg(-1) diet.