Effects of feeding different diets on growth and digestive performance of spotted mandarin fish（Siniperca scherzeri）

【Objective】To study the changes of growth and digestive performance of spotted mandarin fish（Siniperca scherzeri）after feeding on the compound feed，which provided reference for the large-scale culture of S. Scherzeri by using the compound feed instead of the traditional forage fish.【Method】A total of 180 domesticated individuals and 180 undomesticated individuals were fed with compound feed and live forage fish respectively，and starved for 24 h after feeding 20 weeks. The growth performance，digestive enzyme activity，intestinal structure and intestinal microbiota structure of S. scherzeris were determined and analyzed.【Result】After 20 weeks of feeding，the survival rate，viscero-body ratio of S. scherzeri in compound feed group had no significant differences compared with those in live bait group（P> 0.05，the same below），but the final body weight，weight gain rate and feed coefficient were significantly lower than those in live bait group（P<0.05，the same below）. The intestinal α-amylase activity of compound feed group was significantly higher than that of the live bait group，and the trypsin activity was significantly lower，but there was no significant difference in pepsin and lipase activities between the two groups. In addition，the thickness of muscle layer and the height of mucosal folds of S. scherzeri in compound feed group were significantly lower than those in live bait group，but there was no significant difference in the number of intestinal folds between the two groups. In terms of intestinal microbiota， the ACE index and Chao1 index of intestinal microbiota of S. scherzeri in compound feed group were significantly lower than those in live bait group，but there was no significant difference in Shannon index and Simpson index between the two groups. Under the two feeding patterns，Proteobacteria，Firmicutes，Tenericutes and Actinobacteria were the dominant microbiota，and the sum of their relative abundance was more than 98.00%. At the genus classification level，the relative abundance of Burkholderia-Caballeronia-Paraburkholderia in the intestine of S. scherzeri in compound feed group was significantly higher than that in live bait group，while the relative abundance of Sphingopyxis and Mycoplasma of S. scherzeri in compound feed group was significantly lower than that in live bait group.【Conclusion】The growth rate of S. scherzeri decreases significantly when fed with compound feed instead of live bait，and the intestinal structure，digestive enzyme activity and intestinal microbiota structure show adaptive changes. Especially，the feeding of compound feed helps maintain the stability of intestinal microorganisms. In conclusion，it is feasible to breed S. scherzeri with compound feed instead of live bait，but it is necessary to further optimize feed nutrient composition and feeding strategies to improve the growth rate of S. Scherzeri under feeding with compound feed.