Growth, digestive and absorptive capacity and antioxidant status in intestine and hepatopancreas of sub-adult grass carp Ctenopharyngodonidella fed graded levels of dietary threonine

Background: This study was carried out to investigate effects of threonine levels on growth, digestive and absorptive capacity and antioxidant status in intestine and hepatopancreas of sub-adult grass carp (Ctenopharyngodonidella). Results: Weight gain, specific growth rate, feed intake and feed efficiency were significantly improved by dietary threonine (P < 0.05). Intestinal activities of trypsin, chymotrypsin, alpha-amylase, lipase, alkaline phosphatase, gamma-glutamyl transpeptidase and creatine kinase took the similar trends. Contents of malondialdehyde and protein carbonyl in intestine and hepatopancreas were significantly decreased by dietary optimal threonine supplementation (P < 0.05). Anti-superoxide anion capacity, anti-hydroxyl radical capacity, glutathione content and activities of superoxide dismutase, catalase and glutathione-S-transferase in intestine and hepatopancreas were enhanced by dietary threonine (P < 0.05). Conclusions: Dietary threonine could improve growth, enhance digestive and absorptive capacity and antioxidant status in intestine and hepatopancreas of sub-adult grass carp. The dietary threonine requirement of sub-adult grass carp (441.9-1,013.4 g) based on weight gain was 11.6 g/kg diet or 41.5 g/kg of dietary protein by quadratic regression analysis.