Effects Of Different Lipid Sources And Protein Sources On Lipid Metabolism And Protein Metabolism Of Largemouth Bass (Micropterus Salmoides)

1.Effects of different lipid sources and enzymatic hydrolyzed soybean meal on lipid metabolism and protein metabolism of largemouth bassThere are many papers focused on the effect of lipid sources on fatty acid composition and lipid metabolism in fish body,while less information about fatty acid composition change's mechanism in fish muscle.This study investigated the effect of different lipid sources on characteristics of lipid molecules changes in muscle of largemouth bass through biochemical and lipidomics assays,aimed to explore the effect of characteristics of lipid molecules on fish growth performance.Four oils,including solid fish oil(SFO),liquid fish oil(FO)and rapeseed oil(RO)and mixed oil(linseed oil:soybean oil= 1:1)(LSO),were added 12% as fat source in four purified diets with isonitrogenous(46% crude protein)and isoenergetic(21.31 MJ /kg),respectively.480(24.1 ±1.25)g largemouth bass were randomly divided into 4 groups with 3 replications per group,and fed with experimental diets for 103 days.The results showed that the weight gain rate and lipid content of fish body in RO and LSO group were significantly higher than that of SFO and FO group,while the protein content was contrary.This study corroborated that C16: 0and C18:1n-9 were more inclined to deposit the outer position of glycerol skeleton.Besides,there was a competitive relationship between C18:2n-6 and C18:3n-3 in largemouth bass,which resulted in a high accumulation of C18:2n-6 and low accumulation of C18:3n-3in fish body.C18:2n-6 was specifically deposited at the sn-2 position in phosphatidylcholines(PC),and high C18:3n-3 was deposited at sn-2 position in TG.What's more,the positional distribution of highly unsaturated fatty acids(C20:4n-6,C20:5n-3 and C22:3n-6)in triglycerides(TG),PC and phosphatidylethanolamines(PE)molecules were similar,most of which were mainly distributed at the sn-1/ 3 position of the TG molecules and at the sn-2 position in the PC and PE molecules.In general,all of these structural features contribute to utilizing fish lipids towards reducing the negative effects of diets on fish body.2.Effects of replacing fish meal with enzymatic hydrolyzed soybean meal on growth performance,digestive enzyme activity,liver function and metabolism of largemouth bassThe aim of this study was to investigate the effects of replacing fish meal with enzymatic hydrolyzed soybean meal(ESBM)on growth performance,digestive enzyme activity,liver function and metabolism of largemouth bass(Micropterus salmoides).Five isonitrogenous and isoenergetic diets were formulated by replacing fish meal with a plant-based protein source compound(enzymatic hydrolyzed soybean meal: corn gluten meal = 10:1).The additions of ESBM in the feed were 0(E0),15%(E15),20%(E20),25%(E25),30%(E30),replacing 0,23.64%,30.91%,40%,47.27% of the fish meal,respectively.In the additional two diets(SBM and FSBM),soybean meal and fermented soybean meal were used as the substitute for 20% ESBM,respectively.Each group(quadruplicate tanks per group)was fed with one of the diets for 67 days.The results showed that the specific growth rate and weight gain rate of E25 and E30 were significantly higher than those of other groups(P<0.05),but the feed coefficient ratio of each group had no significant difference(P>0.05).The survival rates of the E25 and E30 groups were lower than other group,which may be due to limited feeding rate and small individuals consequently being killed.This may be one of the reasons why the growth performance of the E25 and E30 groups was significantly better than other groups.With the increase of ESBM,the viscerosomatic index,hepatic index and the lipid content of body decreased significantly(P<0.05).When replacing 30.91% fish meal with three kinds of soybean meal,the specific growth rate of FSBM group was significantly lower than that of E20 group(P<0.05),and viscerosomatic index,hepatic index were significantly higher than those of other two groups(P<0.05).Secondly,the activities of amylase and lipase of intestines increased first and then decreased with increment of ESBM in the diets,but they were all significantly higher than that of control group(P<0.05).The activity of pepsin in E20 and E30 group was significantly higher than control group(P< 0.05).When 30.91% fish meal was replaced with ESBM,SBM or FSBM,the activity of amylase in FSBM group was significantly higher than other two groups(P<0.05),while the change of intestinal lipase activity was opposite.Thirdly,all of the activities of total-antioxidant capacity(T-AOC),glutamic oxaloacetic transaminase(AST)and alanine aminotransferase(ALT)in liver were significantly higher than control group(P<0.05)(except for liver ALT in E30 group),while the content of malondialdehyde(MDA)in liver showed a significantly decreasing trend(P<0.05).The content of MDA and the activities ALT in the FSBM group was significantly lower than SBM and E20 group(P< 0.05),and the liver AST activity was in the order of E20>FSBM>SBM.Fourthly,The oxygen consumption increased significantly with the increasing content of ESBM,and the nitrogen excretion in E20,E25 and E30 were significantly higher than E0 group(P<0.05).The nitrogen retention rates of muscle in E20 and E30 were both higher than other groups.Replacing fish meal with ESBM had significant effects on free fatty acid(NEFA),total cholesterol(T-CHO)and triglyceride(TG),low density lipoprotein cholesterol(LDL-C)in serum of largemouth bass.Among E20,FSBM and SBM groups,the oxygen consumption in FSBM group was significantly lower than other two groups(P<0.05),while nitrogen excretion was opposite.The serum T-CHO of SBM group was significantly higher than other two groups(P<0.05),while serum LDL-C and muscle lipid were the contrary trend.The serum TG of E20 group was significantly lower than other two groups(P<0.05).Above all,the addition of ESBM in the diet within 30% would not do harm to the growth,and could lessen the burden of oxidative stress in liver and generally enhance nutrients metabolism.There was the best substitution effect of ESBM when 30.91% of fish meal was replaced with FSBM,SBM and ESBM respectively.3.Using metabonomics to analyze the effects of replacing fish meal with enzymatic hydrolysis soybean meal and soybean meal on metabolism of largemouth bassThe aim of this study was to investigate the regulation mechanism between the growth performance,anti-oxidant capacity and metabolism of the largemouth bass,after replacing fish meal with enzymatic hydrolyzed soybean meal and soybean meal respectively.After the above-mentioned breeding experiment,metabolites in liver of laregemouth bass were analysed by metabonomics.The results showed that: 91 metabolites showed significant differences among E0,E20,and E30 groups,and 81 differential metabolites were identified among E0,E20,and SBM groups.Based on the KEGG pathway analysis of differential metabolites performed by MBROLE 2.0,the following metabolism pathways were significantly influenced by the diets: Alanine,aspartate and glutamate metabolism,Glycine,serine and threonine metabolism,Arginine and proline metabolism,Citrate cycle(TCA cycle),Glyoxylate and dicarboxylate metabolism,Butanoate metabolism,ABC transporters,Pyrimidine metabolism,Glutathione metabolism.In other words,when fish meal was partly replaced with enzymatic hydrolyzed soybean meal and soybean meal,the increase of growth performance and liver anti-oxidant capacity of largemouth bass may associated with energy metabolism,amino acid metabolism.4.Effects of replacing fish meal with enzymatic hydrolyzed soybean meal and soybean meal on the intestinal microflora of the largemouth bassThe topic about the effects of replacing fish meal with plant protein on the intestinal flora of aquatic animals has become a research hotspot in recent years.The aim of this study was to investigate the effects of replacing fish meal with enzymatic hydrolyzed soybean meal and soybean meal on intestinal flora of largemouth bass.The composition of intestinal flora was analyzed by high-throughput sequencing technique.The results showed that:(1)Ace and Chao index in E0 group were lower than other three groups;The shannon index of E20,E30 and SBM groups were higher than that of E0 group,while the simpson index was opposite.(2)On phylum level,Firmicutes,Fusobacteria,Proteobacteria were predominant bacterium in four groups,and Firmicutes were more dominant.On genus level,Clostridium-sensu-stricto-1,unclassified-f-Peptostreptococcaceae,and Cetobacterium were dominant in the intestinal microorganism of largemouth bass.(3)The abundance of Mycobacterium,Pseudomonas and Lactobacillus in E30 were significantly higher than that in other three groups(P<0.05).The relative contents of Vagococcus,Mycobacterium and Alpinimonas were significantly increased in SBM group(P<0.05).In summary,replacing fish meal with enzymatic hydrolysis soybean meal and soybean meal could increase the diversity of intestinal flora in largemouth bass.The addition of enzymatic hydrolysis soybean meal could promote the content of beneficial bacteria,while soybean meal could increase the abundance of harmful bacteria in the intestine.