The Probiotic Mechansim Of Several Diatery Probiotics On Broiler

Microecologics can improve the feed conversion rate, the intestinal histology and the immunesystem of animals, and inhibit the adhesion of pathogenic bacteria through improvement of theintestinal microecology environment of broilers. So far most studies have been focused on the detectionand analysis of apparent traits and physio-biochemical indicators; the molecular mechanism of probioticactions is yet unclear. The objective of this study is to undermine the molecular mechanisms ofprobiotics to improve the growth performance and immune functions of broilers and to provide atheoretical reference for broiler production. Three microecolgoical agents （Bacillus licheniformis,Enterococcus faecium and Clostridium butyricum） were supplemented to the basal diet. By using thetraditional nutrition, microecology, proteomics and bioinformatics, the growth traits, gastrointestinalmicrobiota, and proteomes of broiler fed probiotic or not were analyzed and compared.The results showed that the microecological agents improved the production performance, theimmune functions, the carcass traits and the meat quality of broilers, but varied in extents and aspects.The reason might be that different microecologics have specific growth characteristics. The probioticactions of these tested microecologics to different genders were also different. PCR-DGGE andquantitative PCR analysis showed that microecologics had significant effects on the diversity andpopulation of gut microbiota. By comparison with control groups, supplementation of B. licheniformisresulted in4distinct bands (E. faecium，Pedobacter terricola, Alistipes onderdonkii, and Clostridiummethylpentosum), and the bacterial population showed an upward trend from jejunum, ileum to caecum;E. faecium resulted in10distinct bands (L. saerimneri, L. equi, L. hayakitensis, L. ingluviei，E. faecium[2], C. bartlettii, E. thailandicus, Robinsoniella peoriensis, and Clostridium populeti), and the bacterialpopulation showed an upward-downward trend; and C. butyricum caused16distinct bands (L.salivarius [3], L. agilis [3], L. saerimneri, L. hayakitensis, C. bartlettii, E. cecorum, L. hayakitensis, C.eutactus, C. irregulare, P. terricola, R. peoriensis, and C. populeti), the bacterial population showed thesimilar trend to E. faecium. Of three tested probiotics, C. butyricum showed the most significant effectson gut microbipta by promoting some beneficial bacteria and suppressing some harmful bacteria.The proteomes of intestinal mucosa, liver and breast muscle of AA broiler fed E. faecium wereanalyzed and compared with control group. A total of77protein spots of different abundances weredetected, and68protein spots (88%) were identified. Four proteins PFN2, PLS1, PLS3, and MUC2were closely related to the intestinal structure, which may extend the gut absorptive area and increasethe nutrient absorption efficiency. Down-regulation of immune and antioxidant system-related proteinsindicated that chickens had a stimulated absorption efficiency of nutrients and employed less nutrientsand energy to deal with immune and antioxidant stresses. This proteomic study unravels the molecularunderpin that E. faecium improves intestine structure and immune and antioxidant functions by alteringthe abundances of key proteins of intestinal mucosa.A total of58protein spots of different abundances were detected in the liver proteome, and50protein spots (86%) were identified. Proteins ENO1, ADH6, PCK2, RGN and PGK1were probably involved in carbohydrate metabolism and enhanced the metabolic rate of the pentose phosphate andcitric acid pathways, finally provided more energy and intermediate metabolites. Up-regulation ofBHMT, GOT1, and CTH were closely related to the enhanced metabolic rate of amino acid, andprovided more energy and intermediate metabolites. Up-regulation of ATIC, DPYS, NME4, ALDH1A1and AKR1D1might enhance the metabolic rate of vitamin and provide more intermediate metabolites.Up-regulation of ALB, CAT and GSTM2and down-regulation of LTF, PIT54, FGB, FGG, HSP90B1,and ANXA6probably enhanced the antioxidant and immune functions. The results reveal that E.faecium improved animal growth performance and immune functions by enhancing the metabolic rateand employing less nutrients and energy.In the proteome of breast muscle, there were52protein spots of different abundances, and47proteinspots (90%) were identified. FBP2, GAPDH, LDHA, PGK1, PGM1, PKM2, PAGM1, and PYGL wererelated to carbohydrate and might improve the meat color and pH. Seven cytoskeleton related-proteinsACTN2, MYH1, MYH3, MYH6, MYH7B, MYH9, and ACTB were involved in the improvement oftenderness, flavor, and succulence of meat. The results suggest that E. faecium improved the meatquality by regulating the abundances of key proteins related to carbohydrate metabolism andcytoskeleton assembly.In summary, this study investigated the production performance and intestinal microecology of AAbroilers fed B. licheniformis, E. faecium and C. butyricum and compared their probiotic actions inchickens. Quantitative proteomic analysis of intestinal mucosa, liver and breast muscle identified manykey proteins related to metabolism, cytoskeleton, immune system and antioxidant system. According tothe bioinformatics information, the molecular underpin that probitoics improved growth performance,immune function and meat quality of broilers was revealed at the protein level. This study provides atheoretical reference for microecolgics practice and poultry production and identifies several targetproteins for genetic modification to satisfy human demand on poultry meat.