Abstract: Dietary supplement of polysaccharides from Radix pseudostellariae was studied to determine its effect on the partial non-specific immune function and disease resistance in FFRC strain common carps. The fish were randomly divided into 5 groups, including Group 1 fed with basic diet as control, and Groups 2 to 5 with formulated diet containing 0.1%, 0.2%, 0.3%, and 0.5% of the polysaccharides, respectively. After feeding for 35 d, the content of lysozyme (LZM) and the activities of superoxide dismutase (SOD), acid phosphatase (ACP), and alkaline phosphatase (AKP), as well as the content of serum complement C₃ in the blood of the carps were analyzed. A challenge test was conducted by infecting the carps with Aeromonas hydrophila. The results showed that LZM in Group 2 increased significantly (P<0.05), while the other treatment groups increased extremely significantly (P<0.01), as compared to control. The SOD and AKP activities in the treated fish were higher than those of control. SOD in the carps of Group 3, 4 and 5 were significantly higher (P<0.05),and AKP extremely significantly greater (P<0.01), ACP and serum complement C₃ extremely significantly higher (P<0.01) than those of control. Fish in Group 4 and 5 showed significantly lower mortality against the A. hydrophila infection than control, with an averaged relative survival rate of 54.55%. It appeared that the polysaccharides could enhance the non-specific immunity and disease resistance of the carps, and that the best result achieved with a supplementation of 3 000 mg·kg^-1 in the diet.

Key words: FFRC strain common carp, Radix pseudostellariae polysaccharides, non-specific immune, disease resistance