Effects of traditional Chinese medicines (TCM) on the immune response of grass carp (Ctenopharyngodon idellus)

The use of traditional Chinese medicine (TCM) in aquaculture has been widely investigated. It is believed that herbal supplements could enhance the immunity and promote fish growth. The powdered TCM or its decoction can be easily applied in the form of feed supplements by direct incorporation into fish feeds and side effects are seldom found. In this study, Radix scutellaria (Rs) and Rhizoma coptidis (Rc) showed strong bacterial inhibition on Aeromonas hydrophila out of the sixteen selected herbal extracts. Four TCMs, R. scutellaria, R. coptidis, Herba andrographis (Ha), and Radix sophorae flavescentis (Rsf) were selected to form a compound formulation in the ratio of 1:1:2:3. A feeding experiment on grass carp was conducted with addition of the above TCM formulation (0.5, 1 and 2 % w/w) in the fish feed, and bactericidal activity, total protein and immunoglobulin in blood plasma, and nitroblue tetrazolium activity in the whole blood were measured. 2 % supplementation significantly improved (p < 0.05) the bactericidal activity and total immunoglobulin in the plasma after feeding for 21 days. Compared to control, 2 % TCM feeding groups showed a significantly lower mortality after A. hydrophila challenge at the end of experiment and the same result was archived in field trial. In the cost evaluation, the use of the TCM formulation in grass carp culture was insignificant and could be compensated by improved yield. TCM formulation contained different active ingredients including some immuno-stimulant and antimicrobial agents and therefore could be applicable to multiple diseases. Application of this TCM formulation would be a cost-effective and prophylactic approach for disease control in aquaculture, replacing the use of antibiotics for treating enteritis and even other general diseases.