Effects of different carbohydrate levels in puffed feed on digestive tract morphological function and liver tissue structure of snakeheads (Channa argus)

The major objective of this study conducted for 8 weeks was to investigate the influence of different carbohydrate levels in the feed on the digestion and tissue structure of snakeheads (Channa argus) with prolonged feeding time. The control (CT) group was fed chilled fish, and the experimental groups were fed flour as a carbohydrate source to prepare puffed feed containing 13%, 16% and 19% flour (WS13, WS16 and WS19 respectively). The results demonstrated that carbohydrate levels in the feed had significant effects on amylase activity in the intestinal segment and Na+, K+-ATPase activity in the stomach (p < .05). In all the experimental groups, the pepsin activity in the gastrointestinal tract showed a decreasing trend over time in different feeding cycles. The alkaline phosphatase (AKP) activities in all groups showed a downward trend, and with increased feeding time, AKP in all experimental groups had an increasing trend. The liver index, liver crude fat content and serum triglyceride of snakeheads increased significantly with the increase in carbohydrate content in feed at 4 weeks (p < .05). There were no differences in the stomach structure among the groups as determined using light microscopy. The intestinal villi were injured, and the liver cells became larger and showed damage in a time and carbohydrate level-dependent manner. In conclusion, when the carbohydrate content is too high, it not only affects the morphological function of the snakeheads' digestive tract, but also affects the normal structure of liver cells and the metabolic function of the liver.