Cottonseed protein concentrate as an effective substitute to fishmeal in pike perch (Sander luciperca) feed : Evidence from growth performance, intestinal responses of immune function and microflora

Ze Fan ^1* Jie Zhao ¹ Jiaming Huang ² Cuiyun Lu ¹ Di Wu ¹ Zhipeng Sun ¹ Liansheng Wang ¹ Jinnan Li ¹ Xianhu Zheng ¹

• ¹ Heilongjiang River Fisheries Research Institute, Harbin, China
• ² Guangdong Evergreen Feed Industry Co., Ltd., Zhanjiang, China

The aim of this study was to assess the response characteristic of intestinal immune function and microflora of pike perch (Sander luciperca) on cottonseed protein concentrate(CPC) as a substitute for fish meal. A basal diet was formulated to contain 55% fishmeal, and then CPC was used to replace 0% (CPC0), 20% (CPC1), 40% (CPC2), 60% (CPC3) of dietary fishmeal. The four diets were fed to pikeperch with initial body weight of 3.55 ± 0.01 g for 8 weeks. Results revealed that there were no significant effects of dietary CPC levels on survival rate, mass gain rate and specific growth rate. The maximal value of feeding efficiency ratio was presented in CPC3 group and was significantly higher than that of the control group.Significantly lower value of hepatosomatic index and crude ash content and higher crude protein content were observed in CPC3 group. Trypsin activity in CPC3 group was reduced to the lowest level compared to the control group and CPC1 group. Among three CPC substitution groups, increments in the intestinal antioxidant enzymes activities, glutathione content and anti-inflammatory factor expression and down-regulation in pro-inflammatory factors were observed with increasing CPC substitution. Injury degree of intestinal mechanical barrier was mitigated in step with relief of oxidative damage and inflammation as increasing CPC substitution ratio. Conclusively, 60% fishmeal could be basically replaced by CPC based on the above results. However, increasing dietary CPC substitution slightly increased Firmicutes abundance and obviously decreased Actinobacteriota abundance, but the abundance of Proteobacteria in CPC3 group was appreciably elevated. The elevation of Staphylococcus and the reduction of Lactobacillus were observed in the CPC2 and CPC3 groups. igf1 expressions were significantly down-regulated with increasing CPC substitution. Henceforth, the above two limit factors should be considered as key breakthroughs improving the utilization effectiveness of CPC replacing fish meal for pikeperch. The current findings provided the ponderable reference and breakthrough in improving the application effectiveness of CPC replacing fish meal for pikeperch.