Effects of dietary fishmeal replacement with protein mixtures on growth performance, physiological metabolism and biochemical composition of juvenile Chinese mitten crab (Eriocheir sinensis)

We investigated the effects of different levels (0%, 16.67%, 33.33%, 50% and 66.67%, represented as Diet 1^# to 5^# treatments) of fishmeal replacement by protein mixtures on the survival, growth, physiological metabolism and body biochemical composition of juvenile Chinese mitten crab (Eriocheir sinensis). The results show that: 1) the final body mass, weight gain rate, specific growth rate and hepatosomatic index firstly increased and then decreased with increasing dietary fish meal replacement level, and the highest values were detected in Diet 2^# treatment (P<0.05). 2) The highest levels of glutamic-oxalacetic transaminase (GOT), glutamic-pyruvic transaminase (GPT) and malondialdehyde in hepatopancreas were detected in Diet 4^# treatment, while Diet 1^# treatment had the highest activity of superoxide dismutase (SOD) in hepatopancreas (P<0.05). The highest activity of GPT in the serum was detected in Diet 5^# treatment, and the highest triglyceride (TG) content and SOD activity were detected in Diet 4^# treatment (P<0.05), while the highest malondialdehyde (MDA) content was detected in Diet 2^# treatment. 3) The contents of crude protein and crude lipid in the juvenile crab's body in Diet 1^# treatment were significantly higher than those in the other treatments, while the highest total carbohydrate content was detected in Diet 2^# (P<0.05). For the body amino acids, the highest cysteine (Cys) content was detected in Diet 4^# treatment, and the highest contents of other amino acids and total amino acids (TAA) were detected in Diet 2^# (P<0.05). In conclusion, excessive dietary fishmeal replacement (33%−67%) can reduce the growth performance and accumulation of nutrients in juvenile crab's body, having a negative effect on physiological metabolism. The appropriate dietary fishmeal replacement level is suggested to be about 20%.