Effect of dietary soybean lecithin on growth parameters, digestive enzyme activity, antioxidative status and mucosal immune responses of common carp ( Cyprinus carpio )

Common carp, Cyprinus carpio (13.54 ± 0.48 g), were fed soybean lecithin‐incorporated diets for 8 weeks. After the feeding trials, the different groups of fishes were assessed by survival, growth parameters, digestive enzymes, antioxidant enzyme activities, mucosal immune parameters, etc. The lecithin‐incorporated diets (10–30 g kg –1 ) helped to increase the weight gain significantly ( p  < .05) compared with control groups; activity of digestive enzymes was also significantly ( p  < .05) higher compared with experimental groups. The antioxidant enzymes including catalase and serum superoxide dismutase were significantly ( p  < .05) higher in the C. carpio fed lecithin‐incorporated feed than the ones fed the control feed. The serum thiobarbituric acid‐reactive substances and serum glutathione peroxidase activity did not differ significantly ( p  > .05) between control and experimental groups. The positive correlation supported that antibacterial activity was significantly ( p  < .05) increased with increasing concentration of lecithin in the diets. Among the different mucosal immune parameters, lysozyme, protease and esterase activities were significantly ( p  < .05) increased with lecithin‐incorporated diets. The results of this study confirm that 20 and 30 g kg –1 lecithin inclusion in diets helped to enhance the activities of digestive enzymes, antioxidant enzymes, antibacterial factors and mucosal immune parameters in C. carpio .