Effects Of Different Protein Sources On Liver Transcriptome And Gut Microflora Of Trachinotus Ovatus

Golden pompano(Trachinotus ovatus)is mainly distributed in the south of East China Sea,South China Sea to Southeast Asia sea area,and has become one of the important fish in aquaculture in South China.In recent years,with the rapid development of aquaculture,the supply of fish meal resources is in short supply,resulting in a relatively high proportion of feed cost in the total cost of aquaculture,affecting the development of aquaculture.Therefore,on the premise of no significant impact on fish health and quality,reducing the amount of fish meal in feed and reducing the proportion of feed cost in aquaculture has become a hot research topic in recent years.According to the above problems,two kinds of experimental feeds,were prepared with fish meal(DC)and fermented soybean meal(ZC),as the main protein according to the formula of practical feed for golden pompano.The experimental contents are mainly divided into the following four parts:(1)1800 healthy juveniles golden pompano of the same size and no damage to the body surface were selected,with an initial body weight of(80±2)g.they were randomly divided into 6 cages of3*3*3m.One group of 3 cages was fed with self-made fish meal and fermented soybean meal respectively.After 8 weeks of culture experiment,the fish in each cage was counted and weighed,and the growth performance of each group was calculated.(2)The liver tissues of nine gold pompano were randomly selected from DC and ZC groups,.The transcriptome sequencing technology was used to sequence the transcriptome and compare the gene expression differences;(3)Nine gold pompano with fast growth(120±1g)and stagnant growth(98 ±1g)were selected from ZC group.After sampling liver tissue,the transcriptome sequencing was carried out to analyze the gene expression differences,and the function and pathway of the different genes were studied;(4)Nine gold pompano were randomly selected from the fish meal group and the fermented soybean meal group.Nine of them were selected from the fermented soybean meal group,each of which grew rapidly(120±1g)and slowly(98±1g).The midgut tissues were sampled and sequenced with 16 S r DNA to analyze the differences of intestinal microflora among different products.The culture result show that juveniles golden pompano fed with fish meal,the survival rate was 98.66%,the weight gain rate was 89.6%,the feed coefficient was2.27 and the fatness was 3.89%.Juveniles golden pompano fed with fermented soybean meal,The survival rate was 97.66%,the weight gain rate was 18.8%,the feed coefficient was 6.3,and the fatness was 2.15%.It can be seen from the comparison that the replacement of fish meal with fermented soybean meal has no significant effect on the survival rate of pomfret,but it significantly reduces the growth performance of pomfret,such as the growth rate,feed coefficient,and fatness.Compared with fish meal group,2241 genes in fermented soybean meal group changed(P value < 0.05,the difference is more than 2 times),among which 1076 genes were highly expressed and 1165 genes were low expressed.Through GO annotation and enrichment analysis of KEGG pathway,it was found that the function of differentially expressed genes was related to endoplasmic reticulum protein processing,steroid biosynthesis,protein transport,starch and sucrose metabolism.Comparing the gene expression levels of different growth individuals in fermented soybean meal group,we found that 1026 genes had changed in the gene expression levels of slow growth individuals and fast growth individuals(P value < 0.05,the difference was more than 2 times),including 358 genes with high expression and 668 genes with low expression.Through go function annotation and KEGG pathway enrichment analysis of all significant differentially expressed genes,it was found that the functions of a large number of differentially expressed genes were related to oxidative phosphorylation,steroid biosynthesis,glyceride metabolism,alanine,aspartic acid and glutamate metabolism.The acquisition of these differential genes laid a foundation for revealing the molecular mechanism of growth and development,cloning and expression of growth related genes,and also provided gene data for subsequent biological research.By comparing the 16 S r DNA sequencing results of the samples,we can see that the total number of intestinal flora out in the fish meal group is relatively higher than that in the fermented soybean meal group,but the Shannon,Chao1 and ACE indexes are relatively lower.The diversity of gut microflora in fast growing individuals was greater than that in slow growing individuals.The results of species annotation showed that at the level of taxonomic classification,the top four taxonomic categories in the number distribution of all samples were the same,namely Proteobacteria,Tenerictes,Spirochaetes and Firmicutes,among which the distributionof Proteobacteria in each sample was relatively stable at about 27%,but Tenerictes,Spirochaetes and the distribution of Firmicutes were significantly different among the experimental groups.At the level of genus classification,the significant differences between fish meal group and fermented soybean meal group were gueglia,grimontia,Klebsiella,alistipes,staphyococcus and parasutterella.Brevinema,Ruegeria,Unidentified lachnospiraceae and Blautia were the genera of the differences in fermented soybean meal.The community structure and distribution of the gut microflora of gold pompanus were studied.