Growth performance, intestinal morphology, hepatopancreatic antioxidant capacity and growth-related gene mRNA expressions of juvenile grass carp (Ctenopharyngodon idellus) as affected by graded levels of dietary arginine

An 8-week growth trial was conducted to investigate the effects of dietary Arg levels (7.6, 12.3, 17.9, 22.4 and 28.6 g/kg diet) on growth performance, hepatopancreatic antioxidant capacity, intestinal morphology and growth-related gene expressions of juvenile grass carp (Ctenopharyngodon idellus). The results showed that SGR in Arg22 and Arg28 groups was lower than in Arg12 and Arg17 groups (p < 0.05). Serum NO content in Arg7 group was lower than other groups. Hepatopancreatic GSH-Px activity was higher in Arg17 group than in Arg7 group, while MDA content showed the opposite trend. Hepatopancreatic IGF-1 expression tended to increase with Arg from 7.6 to 22.4 g/kg and then decreased in Arg28 group (p < 0.05), while IGFBP-1 expression increased with Arg level. Muscle mRNA expressions of TOR and S6K1 showed quadratic trends as dietary Arg level increased, which were higher in Arg17 group than in Arg22 and Arg28 groups (p < 0.05). Higher mRNA expression levels of y(+)LAT1, y(+)LAT2 and PepT1, as well as higher villus height and villus width in foregut, were all observed in Arg17 group. The optimal dietary Arg level based on SGR by the quadratic model was 15.3 g/kg diet for juvenile grass carp, corresponding to 54.7 g/kg dietary protein.