Effect of dietary enzyme-treated soy protein on the immunity and antioxidant status in the intestine of juvenile Jian carp (Cyprinus carpio var. Jian)

This study was conducted to evaluate the hypothesis that enzyme-treated soy protein (ETSP) can save the fish dietary protein, and further investigated the mechanism for saving effect by studying the effects of ETSP on intestinal immune response and antioxidant status in juvenile Jian carp (Cyprinus carpio var. Jian). Compared with the high-protein diet, results showed that decreasing 2% of dietary protein increased the protein carbonyl (PC) content, decreased the anti-hydroxyl radical capacity (AHR) and superoxide dismutase (SOD) activity and increased the relative expressions of pro-inflammatory cytokine (p 0.05). The low-protein diet might impair the intestinal health, so as to reduce fish growth performance. After adding 1.5% or 2% of ETSP to the low-protein diet, results indicated that (1) ETSP decreased the relative expressions of pro-inflammatory cytokine and increased the relative expressions of anti-inflammatory cytokine (p 0.05). (2) ETSP decreased malondialdehyde (MDA) and PC content (p 0.05), improved activities of antioxidant enzymes, glutathione (GSH) content, relative expressions of antioxidant enzymes and Nrf2, which were even much higher than the high-protein diet (p 0.05). All the above data suggested that optimal level of ETSP can save 2% of fish dietary protein which might be partly attributed to improve intestinal health through regulating intestinal immunity response and antioxidant status.