Study On The Metabolic Effect Of Taurine Supplementation On Fish Liver And Intestine By NMR-based Metabolomics

With the development of the global aquaculture industry,fish feed nutrition research has received more and more attention.Fishmeal is a good source of protein for aquafeeds.In recent years,there has been a shortage of fishmeal worldwide due to environmental degradation,overfishing,and increased demand.Therefore,people use plant protein instead of fish meal to reduce the cost of aquaculture,but the plant protein is not balanced and lacks trophic factors.Adding an appropriate amount of taurine to the vegetable protein source feed can improve the adverse effects on plant growth caused by plant protein substitution.Nowadays,most studies focus on the analysis of fish growth,body composition and immunology by adding taurine to feed,and less discussion on the metabolic changes and growth mechanisms of different fish caused by taurine.In this thesis,two important economic fishes,Epinephelus coioides and Oreochromis nilotictus,were used as research objects,and nuclear magnetic resonance(NMR)techniques combined with multivariate statistical analysis of metabolomics were used to study.The aims are researching effect of different levels of taurine on the metabolome of these two different fishes,revealing the metabolic mechanism closely related to the growth of fish caused by taurine addition,and to provide scientific basis for the scientific formulation of taurine in fish feed and fisheries nutriology.The main research contents are as follows:1.Research on the metabolic response of grouper liver to different dietary taurine levels during different feeding periods.In the experiment,four kinds of taurine levels(0%,0.5%,1.0%and 1.5%)were prepared for feed for 84 days based on the feed protein source without taurine.The ~1H NMR technique was used to detect the metabolic profiles of fish liver under different periods and different levels of taurine.Combined with multivariate statistical analysis methods,the metabolic differences in different periods and different taurine levels were obtained.The experimental results showed that alanine,asparagine,glycine,histidine,proline,glycerophosphocholine,phosphorylcholine,succinate,malate and a-glucose in the liver of the taurine-added group.A total of 26 metabolites produced significant changes.These metabolite changes mainly involve energy metabolism,amino acid metabolism,glycerophospholipid metabolism,and nucleotide metabolism.Combined with the growth performance and metabolic changes of grouper,the optimum amount of taurine added during the different feeding periods at 28,56 and 84 days were:1.5%,0.5%and 1.0%.The experimental results revealed that taurine has a positive regulation effect on the growth of grouper liver and grouper liver metabolism.2.Research on the metabolic changes of tilapia intestine to different dietary taurine levels during different feeding periods.On the basis of the previous research,tilapia was used as the research obj ect,and the four taurine levels of 0%,0.4%,0.8%and 1.2%were fed for 84 days.The 1H NMR technique was used to detect the metabolic profiles of fish intestines under different periods and different levels of taurine.Combined with multivariate statistical analysis methods,the metabolomic changes of tilapia intestine induced by different taurine levels were obtained.The study found that there are 32 kinds of metabolism of a-glucose and ?-glucose,lactic acid,ethanol,alanine,glutamate,leucine,isoleucine and valine in the fish intestine of the taurine-added group.Things have more significant changes.These metabolite changes mainly involve energy metabolism,amino acid metabolism,glycerophospholipid metabolism,and nucleotide metabolism.Combined with the growth performance and metabolic changes of tilapia,the optimal amounts of taurine in the different feeding periods at 28,56 and 84 days were:0.8%,0.8%and 1.2%,respectively.The experimental results revealed that taurine has a positive effect on the growth and tilapia intestine metabolism.