Effect of dietary copper on the growth performance, non-specific immunity and resistance to Aeromonas hydrophila of juvenile Chinese mitten crab, Eriocheir sinensis

An 8-week feeding trial was conducted to determine the dietary copper (Cu) on growth performance and immune responses of juvenile Chinese mitten crab Eriocheir sinensis. Six semi-purified diets with six copper levels (1.88, 11.85, 20.78, 40.34, 79.56 and 381.2 mg kg^-1 diet) of CuSO₄·5H₂O were fed to E. sinensis (0.45 ± 0.01 g). Each diet was fed to the crab in five replicates. The crab fed diets with 20.78 and 40.34 mg Cu kg^-1 diet had significantly greater weight gain and hemolymph oxyhemocyanin content than those fed diets with 1.88 and 381.2 mg Cu kg^-1 diet. Survival rates of crab were not significantly different between all treatment groups. The activities of copper-zinc superoxide dismutase (Cu-Zn SOD), phenoloxidase (PO), and total hemocyte count (THC) significantly increased when the supplementation of dietary copper reached 20.78-40.34 mg Cu kg^-1 diets. In the bacteria challenge experiment with Aeromonas hydrophila, survival rates significantly increased and reached a plateau when the dietary copper increased from 1.88 to 40.34 mg kg^-1, whereas significantly decreased when the dietary copper increased from 40.34 to 381.2 mg kg^-1. This study indicates that the level of dietary copper is important in regulating growth and immune response in crab.