Effects of dietary dextrin level on growth performance, feed utilization, biochemical composition, digestive enzyme activity, antioxidant capacity and tissue structure of juvenile Onychostoma macrolepis

Effects of dietary dextrin at inclusion levels of 14.7 %, 20.7 %, 26.7 %, 32.7 % and 38.7 % on growth performance, feed utilization, biochemical composition, digestive enzyme activity, antioxidant capacity and tissue structure of Onychostoma macrolepis (1.78 +/- 0.10 g) was evaluated, the trial was conducted for 56-day. The results revealed that final body mass, weight gain and protein efficiency ratio were the highest in the 26.7% group, while feed conversion ratio (FCR) was the opposite. The optimal values of FCR and specific growth rate (SGR) were 25.27 % and 25.67 % respectively based on the quadratic regression analysis. The hepatopancreas trypsin activity was the lowest in the 32.7 % group (P<0.05), while the lipase activity in the 14.7 %, 20.7 %, and 26.7 % groups were higher than remaining groups (P<0.05), however, the amylase activity was not affected (P>0.05). Only the crude protein of whole fish was affected, its content was the highest in the 32.7 % group. Hepatopancreas and muscle glycogen were the highest in the 26.7 % group (P<0.05). Combined with the systematic clustering average method was found that MUFA and SFA in hepatopancreas increased, and n-6 PUFA and MUFA in muscle and MUFA in abdominal fat decreased with dextrin levels. The hepatopancreas glutathione peroxidase activity in the 32.7 % group was the lowest and catalase activity in the 20.7 % group was the highest (P<0.05), total superoxide dismutase activities in the 14.7 %, 20.7 % and 26.7 % groups were significantly higher than remaining groups (P<0.05), and malonaldehyde content in 38.7 % group reached the highest (P<0.05). Hepatopancreas exhibited severe vacuolation in the 32.7 % group, and intestinal villi were the longest in the 26.7 % group (P<0.05). In summary, based on FCR and SGR, the optimal dextrin levels in Onychostoma macrolepis feed were 25.27 % and 25.67 % respectively. When having good growth and not negatively affecting health status, the recommended addition levels of dextrin in feed were 20.7-26.7 %.