| Common carp（Cyprinus carpio）is one of the most important freshwater fish with an enormous nutrition and delicious meat in China.Under the condition of water quality deterioration,feed metamorphism and environmental stress,the cultured fish represented by carp can easily cause bacterial intestinal diseases,which hinders the sustainable development of aquaculture industry.Therefore,exploring the pathogenic mechanism of carp bacterial intestinal diseases and finding effective preventive measures and methods have been the focus of research on disease prevention and control of farmed fish in recent years.Probiotics have attracted extensive attention because of their advantages of safety,environmental protection,easy access and low cost.This study aims to explore the effects of compound probiotics on carp intestinal health,growth performance and meat quality.The main research results are as follows:1.Based on RNA-seq,this study explored the regulation of bacterial LPS on the pathogenic mechanism of carp intestinal epithelial cells.In this study,intestinal epithelial cells of carp were taken as the research object.Normal treatment was the control group,and LPS treatment was the experimental group.RNA-seq was performed on the two groups of intestinal epithelial cells treated for 24 h.A total of44.77 G of high-quality data were obtained from RNA-seq results,of which,nearly 81.83% data could be compared to the carp genome.Using the Deseq software analysis to discover,compared with the control group,590 differentially expressed genes（DEG）were induced by LPS treatment.Among them,303 were up-regulated and 287 were down-regulated.GO functional enrichment analysis showed that DEG accounted for the highest proportion in cellular processes,cells and binding functional subclasses.The KEGG pathway analysis revealed that DEG was significantly enriched in cell cycle,autophagy and apoptosis pathways.In this study,RNA-seq was used to comprehensively and rapidly obtain all transcriptome information during LPS exposure to carp intestinal epithelial cells,and to systematically prove that LPS blocked the cell cycle of carp intestinal epithelial cells,induced autophagy and apoptosis,thus providing an important theoretical basis for the molecular mechanism of LPS regulation in carp intestinal epithelial cells.2.In this study,pathogenic bacteria（Aeromonas hydrophila）were isolated and purified from the intestinal tract of diseased carp,and the health carps were divided into 4 groups: control group,control group + probiotic group,A.hydrophila group and A.hydrophila + probiotics group.The purpose is to explore the effects of compound probiotics on intestinal autophagy,apoptosis,immunity,barrier mechanism and microflora.The results showed that,compared with the control group,dietary compound probiotics could significantly increase the expressions of TLR4,IL-10 genes and the activities of ACP and LZM enzymes in the intestine of carp.In addition,dietary compound probiotics can improve the diversity of intestinal flora and maintain the integrity of the intestinal barrier structure by reducing the abundance of the intestinal Proteobacteria and increasing the abundance of Firmicutes and Fusobacteria.Not only that,the study also found that dietary compound probiotics can effectively inhibit the over-expression of intestinal autophagy（LC3II,ATG16）,apoptosis（CASP3,Bax）and inflammatory（IL-1β）gene caused by A.hydrophila.By regulating the damage of intestinal barrier function and disturbance of intestinal flora caused by A.hydrophila,the intestinal health of carp was improved.3.This study was conducted to evaluate the effects of compound probiotics on growth performance and meat quality of carp.The results showed that compared with the control group,dietary compound probiotics could not only improve the growth performance（WGR and SGR）,but also increase the contents of protein and amino acids（glutamic,glycine,leucine and isoleucine）in the muscle of carp.Importantly,this study also found that dietary compound probiotics significantly improved the decrease of A.hydrophila induced growth performance（WGR,SGR,FCR and SR）.By inhibiting the decrease of protein,lipid and amino acid content in muscle caused by A.hydrophila,the meat quality of carp was improved.In conclusion,the present study found that the bacterial intestinal disease of carp is closely related to the cell cycle,autophagy and apoptosis pathways.Dietary compound probiotics can significantly improve the intestinal health,growth performance and meat quality of carp.This study not only provides a solid theoretical basis for the frequent bacterial intestinal diseases of carp,and provides an important scientific basis for the subsequent commercial promotion and application of compound probiotics in aquaculture industry. |
