Effects of dietary protein level on the growth performance, feed utilization and immunity of red swamp crayfish Procambarus clarkia

Abstract

A 8-week feeding trial was conducted to determine the dietary protein requirement of red swamp crayfish, Procambarus clarkia (5.17 ± 0.32 g), as well as the effects of different dietary protein (26 %, 28 %, 30 %, 32 % and 34 %) on the growth performance, feed utilization, digestive enzymes activity and immunity of P. clarkia. Each diet was fed to four replicate tanks of P. clarkia in a re-circulated water system, and each replicate had 40 prawns. Results showed that P. clarkia fed with 32 % and 34 % dietary protein had significantly higher final weight, weight gain rate and specific growth rate than that fed with 26 % and 28 % dietary protein (P < 0.05), but no significant difference was found in survival rate among all groups (P> 0.05). The feed coefficient rate of P. clarkia fed with 34 % dietary protein was the highest (P < 0.05), the protein efficiency ratio and the muscle protein content of P. clarkia fed with 26 % dietary protein was the lowest (P < 0.05). Different dietary protein level had no significant effect on the hepatosomatic index and viscerosomatic index of crayfish (P> 0.05), but the condition factor of P. clarkia fed with 26 % dietary protein was significantly lower than that fed with 32 % and 34 % dietary protein (P < 0.05). With the dietary protein level increased, the pepsin and trypsin activity were significantly increased (P < 0.05), and the highest amylase activity was found in P. clarkia fed with 34 % dietary protein (P < 0.05). Moreover, higher dietary protein significantly increased the antioxidant and antibacterial activity (P < 0.05). Based on the WGR and SGR, broken-line analysis showed that dietary protein requirements of P. clarkia were 31 % in the present study.