Dietary salidroside and astragalus polysaccharides enhance the growth performance and hypoxia tolerance of juvenile Chinese mitten crabs (Eriocheir sinensis)

This study investigates the effects of salidroside and astragalus polysaccharides on growth performance and hypoxia tolerance of juvenile Chinese mitten crabs (Eriocheir sinensis). A total of 1200 crabs (0.23 ± 0.01 g) were randomly allocated to 5 groups, each with 6 replicates of 40 crabs. Crabs were fed isonitrogenous and isolipidic diets containing 0 (control), 300 or 600 mg/kg salidroside (S300 or S600), 300 or 600 mg/kg astragalus polysaccharides (A300 or A600) for 8 weeks. After feeding trial, each group underwent a 24-h hypoxia stress with dissolved oxygen maintained at 2.0 ± 0.2 mg/L. The weight gain of A600 group has significantly increased. Hypoxia significantly reduced the oxygen consumption rate and hemocyanin content. In contrast, S300 group exhibited a significant increase in hemocyanin content, whereas A600 group showed a significant decrease in oxygen consumption rate. S300 group showed significant increases in glycogen content and cpt1 expression, whereas lactic acid and triglyceride contents significantly decreased. Supplementation with 600 mg/kg astragalus polysaccharides reduced glycogen and triglyceride contents at different oxygen levels. Salidroside significantly reduced malondialdehyde content, it also increased glutathione peroxidase and superoxide dismutase activities. Under hypoxia, only A600 group increased alkaline and acid phosphatase activities compared to the control group. Thus, salidroside and astragalus polysaccharides effectively increased hypoxia tolerance by reducing the oxygen consumption rate, improving energy metabolism, strengthening antioxidant capacity and regulating immune responses. Based on these findings, dietary supplementation with 300 mg/kg salidroside or 600 mg/kg astragalus polysaccharides is recommended to improve crab growth performance and hypoxia tolerance.