Effects Of Dietary Curcumin Supplementation On Growth,Intestinal And Liver Health Of Juvenile American Eel(Anguilla Rostrata)

This experiment was conducted to evaluate the effects of different dietary curcumin supplementation levels on the growth performance,serum biochemical parameters,and the health parameters of intestine（Digestive enzymes activities,morphology,and flora composition）and liver（Antioxidant potential,inflammatory factors,lipid metabolism enzymes,morphology,and metabolites）of American eel（Anguilla rostrata）juveniles.TrialⅠEffects of dietary of curcumin supplementation on the growth,biochemical parameters,intestinal health and liver health of juvenile American eelSix hundred healthy American eel juveniles with average body weight of 12.28±0.02 g per fish were randomly divided into five treatment groups with four replicates per group.The five groups were fed commercial diet（CUR0 group）and commercial diet supplemented with curcumin levels of 100 mg/kg（CUR100 group）,200 mg/kg（CUR200 group）,300 mg/kg（CUR300 group）,and 400 mg/kg（CUR400 group）,respectively.The trial period was 10 weeks.Dietary curcumin supplementation significantly increased the final body weight,weight gain rate,specific growth rate,protein efficiency ratio,and feed efficiency of juvenile American eel（P<0.05）;the hepatosomatic index,viscerosomatic index and survival rate were not significantly affected（P>0.05）.Serum acid phosphatase,alkaline phosphatase and lysozyme activities,and high density lipoprotein cholesterol,immunoglobulin M and complement 3 levels were significantly increased by curcumin supplementation（P<0.05）,and the values of these parameters in CUR200 group were the best among all the groups.The levels of blood urea nitrogen,triglyceride,total cholesterol,low density lipoprotein cholesterol,and D-lactate,and glutamic-oxalacetic transaminase,glutamic-pyruvic transaminase,lactate dehydrogenase and diamine oxidase activities were significantly decreased by curcumin supplementation（P<0.05）,and the values of these parameters in CUR200 group were the lowest among all the groups.The crude lipids content of the whole fish body was significantly decreased by curcumin supplementation（P<0.05）.Dietary curcumin supplementation significantly increased intestinal lipase and amylase activities of juvenile American eel（P<0.05）,and lipase activities were increased firstly and then decreased with the increasing curcumin levels,the value in CUR200 group was highest.Compared with CUR100,CUR300 and CUR400 groups,amylase activities of CUR200 group were significantly increased（P<0.05）,there was no significant difference among the CUR100,CUR300 and CUR400 groups（P>0.05）.No significant difference in protease activities was found among all the treatment groups（P>0.05）.Villus height and muscular thickness were significantly increased by curcumin supplementation（P<0.05）,and there was no significant difference among the curcumin supplementation groups（P>0.05）.Compared with CUR0 group,the diversity and richness of intestinal flora were reduced.At phylum level,the relative abundances of Tenericutes,Proteobacteria,Firmicutes and Fusobacteria were decreased,while the relative abundance of Spirochaetae was increased of the intestinal flora in the CUR200 group.At the genus level,the relative abundances of Curvibacter,Clostridium-sensu-stricto,Bradyrhizobium,Kocuria,Lactococcus,Ornithinmicrobium and Enterococcus were significantly increased in CUR0 group（P<0.05）,Caulobacter and Brevinema were significantly increased in CUR200 group（P<0.05）.Dietary curcumin supplementation significantly improved liver superoxide dismutase activities,total antioxidant capacity and reduced glutathione levels（P<0.05）,and the malondialdehyde level was significantly decreased by curcumin supplemeantion（P<0.05）.Total antioxidant capacity of CUR200 group were significantly higher than those of CUR100,CUR300 and CUR400 groups（P<0.05）,there was no significant difference among the CUR100,CUR300,and CUR400 groups（P>0.05）.With the increasing curcumin supplementation,superoxide dismutase activities and reduced glutathione levels increased firstly and then decreased,while malondialdehyde levels trended to decrease firstly and then increased.There was no significant difference in catalase activities among all the groups（P>0.05）.The levels of interleukin 1β,interleukin 8,tumor necrosis factorαand Interferonγof liver in curcumin supplementation groups were significantly decreased（P<0.05）.The lipoprotein lipase,hepatic lipase and total lipase activities of liver were significantly increased（P<0.05）,and fatty acid synthetase activities were significantly decreased by curcumin supplementation（P<0.05）.Compared with the CUR0 group,the pathways enriched by differential metabolites were mainly related to the metabolism of amino acids in the liver of the CUR200 group.The amino acid metabolism pathway mainly included glutathione metabolism,valine,leucine and isoleucine biosynthesis,glycine,serine and threonine metabolism,histidine metabolism,arginine and proline metabolism.Vitamin metabolism was related to biosynthetic pathway of ubiquinone and other terpene quinones.Sugar metabolism was related to galactose metabolism.The bright value（L*）and yellow value（b*）of belly skin in the CUR100,CUR200 and CUR300 groups were significantly increased by curcumin supplementation（P<0.05）.There was no significant difference in dorsal body color parameters and abdominal redness values among all the groups（P>0.05）.The maximum difference of body color between dorsal and abdomen was found in CUR200 group.TrialⅡAlleviation effects of dietary curcumin supplementation on liver injury the induced by CCl₄ to juvenile American eelAt the end of above feeding experiment,24 American eel with the same specifications were selected from the CUR0 group and divided into the blank group（injected with the same dose of olive oil）and the control group（with a dose of 0.05 m L/10 g,intraperitoneal injection of 30%CCl₄-Olive oil solution,CCl₄+CUR0 group）with twelve fish per group.Twelve selected fish from CUR100,CUR200,CUR300 and CUR400 groups were injected intraperitoneal with 30%CCl₄-Olive oil solution,respectively,and they were named as CCl₄+CUR100 group,CCl₄+CUR200 group,CCl₄+CUR300 group and CCl₄+CUR400 group,respectively.The samples of fish without feeding were collected after 72 hours.Hepatosomatic index,serum transaminase activities and liver malondialdehyde levels were significantly increased by injection of 30%CCl₄-Olive oil solution after 72 hours（P<0.05）,while total antioxidant capacity,reduced glutathione levels,superoxide dismutase and catalase activities in liver were significantly decreased（P<0.05）.With the increasing levels of curcumin supplementation,hepatosomatic index was increased firstly and then stabilized,serum glutamic-oxalacetic transaminase and glutamic-pyruvic transaminase activities were decreased firstly and then increased,liver reduced glutathione levels and superoxide dismutase activities were increased firstly and then decreased,and catalase activities were increased firstly and then stabilized,malondialdehyde levels decreased first and then increased.The health status in liver was best in CUR200 group.In conclusion,curcumin could promote the growth of American eel juveniles,reduce body fat accumulation and blood lipid levels,improve serum non-specific immune,increase digestive enzyme activities,and regulate intestinal flora composition and tissue morphology of intestine.It could improve the antioxidant capacity,reduce the level of inflammatory factors,increase the activity of catabolic enzymes and reduce the activity of anabolic enzymes of liver,regulate the metabolism of amino acids,vitamins and sugars,improve the body color of juvenile American eel in a certain extent,and alleviate the liver injury induced by CCl₄.It was recommended that the supplementation level of curcumin in diet of American eel should be 229.58-235.50 mg/kg based on optimal weight gain ratio and feed efficiency.