Effects of Astragalus polysaccharides on antioxidant abilities and non-specific immune responses of Chinese mitten crab, Eriocheir sinensis

This study assessed the effects of Astragalus polysaccharides (APS) on antioxidant abilities, non-specific immune responses, and immune protective efficacy (attacked by Aeromonas hydrophila) of Eriocheir sinensis, the most important Chinese freshwater crabs. A total of 720 crabs (initial mean weight 10.27 +/- 1.58 g) were fed 60 days with six kinds of experimental diets containing graded dosages of APS (0, 300, 600, 900, 1200, 1500 mg/kg diets) in 18 outdoor cement tanks. The results showed that superoxide dismutase (SOD), catalase (CAT), total antioxidant capacity (T-AOC), lysozyme (LZM), and phenoloxidase (PO) activities of serum significantly increased (P < 0.05) with increasing APS dosages (0-900 mg/kg diets), but alkaline phosphatase (AKP) and acid phosphatase (ACP) activities of serum did not significantly changed (P > 0.05); SOD, CAT, T-AOC, LZM, AKP, and ACP activities of hepatopancreas significantly increased (P < 0.05) with increasing APS dosages (0-1200 mg/kg diets); the increased maximal multiples of LZM and PO activities were higher than SOD, CAT, and T-AOC which increased. The results of A. hydrophila attack test showed that mortality rates significantly decreased (P < 0.05) with increasing APS dosages (0-600 mg/kg diets), and the highest immune protective rate was 49.4%. In short, APS could help E. sinensis to improve immune responses and may reduce the risk of disease attacks as one kind of effective immunopotentiator in diets, and the best additive dosage was 1200 mg/kg.