Partial or complete substitution of fish meal with soybean meal and cottonseed meal in Chinese mitten crab Eriocheir sinensis diets

The practical level of fish meal replacement by plant proteins in aquaculture feed varies greatly among species. This study investigated partial or complete replacement of fish meal (FM) by cottonseed and soybean meal (CS) in Chinese mitten crab Eriocheir sinensis. Cottonseed and soybean meals were equally mixed to form five isonitrogenous and isocaloric diets to replace 0 (CS0, control), 21 % (CS21), 43 % (CS43), 64 % (CS64), and 100 % (CS100) of FM. The highest crab growth and feed utilization were observed in the CS21 diet, followed by the CS43 diet. Crab fed CS64 had similar weight gain, specific growth rate, feed conversion ratio, protein efficiency ratio, protein retention and energy retention to those fed the control diet. Dry matter digestibility decreased with increasing dietary CS and was significantly lower in the CS64 and CS100 treatments than in the control. Apparent protein and energy digestibilities of the crab fed CS0, CS21, or CS43 were similar but significantly higher than the crab fed CS64 or CS100. Crab fed CS100 had poorer digestibility of nutrients than those fed other diets. The dry matter of the crab fed CS21 was significantly higher than the crab fed CS100. The protein contents in crabs fed CS21 or CS43 were similar but were higher than those fed other diets. Crab fed CS21 contained higher lipid and gross energy than in other treatments. This study indicates that 64 % of FM can be replaced by CS in crab diet without compromising growth performance and body composition.