Search

The current study was conducted to determine the effects of dietary Radix bupleuriroot extract (RBE) on the growth performance, muscle composition, immune responses, and microcystin-LR (MC-LR) stress resistance of juvenile red claw crayfish (Cherax quadricarinatus). Crayfish (0.28 ± 0.02 g) were fed experimental diets containing graded RBE levels as 0 (Diet 1), 0.2 (Diet 2), 0.4 (Diet 3), 0.6 (Diet 4), 0.8 (Diet 5) and 1.6 (Diet 6) g/kg RBE for 8 weeks. The results showed that specific growth rate (SGR) and weight gain rate (WGR) were significantly increased in the Diet 4 and Diet 5 groups. The content of muscle crude protein was significantly increased in the Diet 4 and Diet 5 groups, and the crude lipid content was significantly decreased in the Diet 5 group. Dietary RBE did not alter the structure of the hepatopancreas. Total antioxidant capacity (T-AOC) and superoxide dismutase (SOD) activities in hepatopancreas and plasma were significantly increased in Diet 4 and Diet 5 groups compared to the control group, while the malondialdehyde (MDA) content in hepatopancreas and plasma was significantly decreased in the Diet 5 group. Plasma alkaline phosphatase (AKP) activity was significantly higher in the Diet 3, Diet 4, Diet 5 and Diet 6 groups. Hepatopancreas and plasma PO activities were significantly increased in Diet 4 and Diet 5 groups. The mRNA levels of extracellular copper/zinc superoxide dismutase (ecCu, Zn-SOD), hemocyanin, C-type lysozyme (C-LZM), GPx, and selenium-dependent glutathione peroxidase (Se-GPx) were significantly up-regulated in the hepatopancreas of crayfish fed Diet 5 than those of the control group. After MC-LR challenge, the survival rates of crayfish in the Diet 4 and Diet 5 groups were significantly higher than the control group. The findings suggest that 0.6–0.8 g/kg of RBE can improve growth and muscle composition and enhance immunity and microcystin-LR resistance.