Effects of sodium butyrate on growth, digestive enzyme activity, serum biochemical indices and intestinal histology of grass carp (Ctenopharyngodon idella)

The study investigated the effects of dietary supplementation of sodium butyrate on growth performance, intestinal digestive enzyme activity, serum biochemical indices and intestinal morphology of Ctenopharyngodon idella. Based on the control diet (SB0), microencapsulated sodium butyrate (containing 50% sodium butyrate) was added at the levels of 0 mg/kg (SB0), 1 000 mg/kg (SB1), 2 000 mg/kg (SB2) and 3 000 mg/kg (SB3) to form four iso-nitrogenous and iso-lipidic diets, respectively. A total of 300 C. idella juvenile (10.0±0.1) g were randomly divided into 4 groups with 3 replicates (cages) and 25 fish per replicate. The fish were fed the four diets in indoor cement ponds for 8 weeks. The results showed that the weight gain and feed conversion ratio of all groups were 273.7%-279.9%, 1.55-1.60, and dietary sodium butyrate did not significantly affect the growth performance and body composition of C. idella (P>0.05). Compared to the control group (SB0), dietary sodium butyrate significantly increased intestinal protease activity and serum superoxide dismutase (SOD) activity (P<0.05), and decreased serum aspartate aminotransferase (AST) activity (P<0.05). In addition, serum alkaline phosphatase (AKP) activity was increased significantly in SB1 group (P<0.05), while serum alanine aminotransferase (ALT) activity was decreased significantly in SB2 and SB3 groups (P<0.05). There was no significant difference in intestinal amylase activity, serum acid phosphatase (ACP), triglyceride (TG), glucose (GLU), total protein (TP) and D-lactic acid (D-LA) among the four groups (P>0.05). In intestinal and hepatic histology, the supplementation of sodium butyrate significantly increased the height of intestinal villi (P<0.05), and the thickness of muscle layer in SB1 and SB2 groups was significantly higher than that in the control group (P<0.05), but no significant differences in intestinal villus width and hepatic histology were observed among the four groups (P>0.05). In conclusion, dietary supplementation of sodium butyrate did not significantly promote the growth performance of C. idella, but increased the activity of intestinal digestive enzymes and improved the morphology of intestinal tissue.