Effects of anthraquinone extract from rhubarb Rheum officinale Bail on the crowding stress response and growth of common carp Cyprinus carpio var. Jian

A total of 750 common carp, Cyprinus carpio Var. Jian, fingerlings were divided randomly into five groups: a control group on a basal diet, four treatment groups fed a basal diet supplemented with 0.5%, 1.0%, 2.0%, and 4.0% anthraquinone extract, respectively. After 10 weeks, the fish were exposed to crowding stress for I and 7 days. In treated fish before the stress an increase was found in the specific growth rate, fullness coefficient, and activities of blood lysozyme, hepatic catalase and superoxide dismutase, whereas a decrease was observed in the feed conversion rate, hepatic malondialdehyde contents and the mortality rate. Noteworthily, these variations did not show dose-dependency of anthraquinone extract. The blood cortisol, glucose, lysozyme and hepatic malondialdehyde levels significantly increased in all groups after I and 7 days of crowding stress. Amongst those in the control were the highest. At 7 days after crowding stress, the blood cortisol levels and hepatic malondialdehyde contents remained higher in all groups. Additionally, the blood glucose and lysozyme levels decreased to some extent, but still higher than those before stress. The hepatic catalase and superoxide dismutase activities could decrease in all groups after I and 7 days of crowding stress, but the activities in treatment groups, supplemented with 1-2.0% anthraquinone extract, kept higher than those in the control. Before the crowding stress the artificial infection with Aeromonas hydrophila resulted in mortality in all groups except for the groups supplemented with 1-2.0% anthraquinone extract. The present study suggested that ingestion of 1%-2.0% anthraquinone extract supplemented a basal diet has the potential to prevent the pathogenic infection, mitigate the negative effects of crowding stress, and promote growth of the fish. (C) 2008 Published by Elsevier B.V.