Effects of compound plant extracts on growth performance, antioxidant capacity, and histomorphology of liver and intestine of rice field eel (Monopterus albus)

Compound plant extracts (CPE) are beneficial for aquatic animals on growth performance and antioxidant capacity. A 56-day experiment was conducted to investigate its positive effect on rice field eel. The fish were fed a commercial diet and supplementing CPE (mainly containing eucommia polysaccharides, reducing sugar) at 0, 0.8, 1.6, 2.4, and 3.2 g/kg. Results showed that dietary CPE significantly increased weight gain and specific growth rate (p < 0.05). Liver lipid content in 1.6 and 3.2 g/kg groups was significantly lower than in 0.8 and 2.4 g/kg groups (p < 0.05). Muscle lipid content in 0.8, 2.4, and 3.2 g/kg CPE groups was significantly lower than in control (p < 0.05). Meanwhile, intestinal digestive enzymatic activities in the 3.2 g/kg CPE group were the highest in comparison to all other groups (p < 0.05). Dietary CPE enhanced the antioxidant activities of serum and intestine (p < 0.05). Compared with the control, intestinal fold thickness in CPE groups was significantly increased (p < 0.05). Furthermore, dietary CPE reduced the degree of liver steatosis and the number of lipid droplet vacuoles. This study indicated that dietary CPE was beneficial to growth performance, antioxidant capacity, liver, and intestinal histology. Supplementation with 1.6–3.2 g/kg CPE is optimal for this eel species.