Effects of dietary protein level on the growth performance, feed utilization and immunity of red swamp crayfish Procambarus clarkia
Shuyan Miao, Bei Han, Jiaqing Li, Juntao Hu, Wenlong Wan, Longsheng Sun, Zhenhua An
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.