| Bacillus amyloliquefaciens is one type of probiotics which has high homology with Bacillus subtilis.Bacillus amyloliquefaciens has strong adaptability to the environment,it could produce several digestive enzymes and inhibit some pathogenic bacteria.Thus it is widely used in the plant and animal production.In this study,Bacillus amyloliquefaciens TL was administrated into the diet to explore its effect on the growth performance in the early stage of chickens and its influence on the brolier's cecum microbiota.A total of 180 Cobb 500 brolier chicken were selected and divided randomly into three groups.Chicken in the control group were fed with basal diet,and the probiotic group were fed with basal diet supplemented with 200 g/t Bacillus amyloliquefaciens TL,while antibiotic group were fed with basal diet supplemented with 50 g/t aureomycin.Broilers were provided ad libitum access to diets and water and fed until 21 days old.The results of this study are as follows:Body weight: The weight of chickens in the probiotic and antibiotic group showed an increase of 27.06% and 17.65%,respectively,as compared with control(P<0.01),suggesting a growth promoting effect performed by Bacillus amyloliquefaciens TL and aureomycin.Composition of the cecum microbiota: At the phylum level,the relative abundance of Firmicutes in the probiotic and antibiotic group increased significantly(from 51.11% to 89.69% and 93.40%,respectively)compared with control,and was positively related to the body weight of chicken(P<0.01);while the abundance of Bacteroidetes(from 36.87% to 3.61% and 0.17%,respectively)in the two treatment groups decreased significantly compared with control,and were negatively related to weight of chicken(P<0.01).And the taxa at the phylum level showed no difference between probiotic and antibiotic group.At the genus level,there were 9 genera showed significant increase in the two treatment groups than control,such as Lachnoclostridium and Ruminiclostridium(P<0.05);while 4 genera showed significant decrease than control,such as Bacteroides and Parabacteroides(P<0.05).Whereas 8 genera such as Blautia and Pseudoflavonifractor were specifically increased in the probiotic group than control(P<0.05),and 8 genera such as Clostridium and Flavonifractor were specifically enriched in the antibiotic group than control(P<0.05).At the species level,the two treatment groups both had 32 species enriched than control,among which 24 species such as C_leptum and C_methylpentosum showed significant enrichment both in the two treatment groups(P<0.05);while 8 species showed in the opposite way,such as B_vulgatus and B_uniformis(P<0.05).Moreover 8 species such as R_gnavus and D_formicigenerans were specifically enriched in the probiotic group than control(P<0.05);while 8 species such as C_botulinum and C_butyricum were specifically enriched in the antibiotic group than control(P<0.05).and B_ovatus was specifically decreased in the antibiotic group than control(P<0.05).In addition,the potentially pathogenic bacteria including Salmonella_enterica,Escherichia_coli,Shigella_boydii,Shigella_dysenteriae,Shigella_flexneri and Shigella_sonnei showed no significant difference in the three groups(P>0.05),but Staphylococcus_aureus showed significant increase in the antibiotic group compared with control(P<0.05).These results indicated that administration of Bacillus amyloliquefaciens TL and aureomycin shifted the cecum microbiota composition in a similar way,the predominant Bacteroidetes were both replaced by the Firmicutes,and the majority of the increased species from Firmicutes were acetate and butyrate producing bacteria.However,the use of aureomycin increased the relative abundance of C_botulinum and Staphylococcus_aureus which is harmful to the health of broiler chicken.Cecum microbiota fuction: The KEGG subsystems about nutrient metabolism and hazardous substance such as Selenocompound metabolism,Linoleic acid metabolism,Bisphenol degradation and Styrene degradation showed significant enrichment both in the two treatment groups(P<0.05),while Bacterial secretion system,Streptomycin biosynthesis and Flagellar assembly showed significant decrease in the two treatment groups than control(P<0.05).In addition,Benzoate degradation,Ethylbenzene degradation,Nonribosomal peptide structures specifically enriched in the probiotic group than control(P<0.05);while Butanoate metabolism,Chloroalkane and chloroalkene degradation specifically enriched in the antibiotic group than control(P<0.05).Moreover,in the acetate,propionate and butyrate biosynthesis pathway analysis,genes related to acetate,propionate and butyrate biosynthesis tended to increase in the probiotic and antibiotic group compared with control,while genes related to propionate biosynthesis tended to decrease.The CAZy subsystems involved in degradation of acetylxylan,cellobiose and levan including CE4,GH94 and GH32 showed significant enrichment in the probiotic group than control(P<0.05),while subsystems involved in cleaving of xylose,rhamnose and peptidoglycan including GH43,GH78 and GT51 showed in the opposite way(P<0.05).While in the antibiotic group,subsystems involved in degradation of cellulose,acetylxylan and starch including CBM13,CE4 and GT5 increased significantly than control(P<0.05);while subsystems involved in cleaving of peptidoglycan and xylose including GH23 and GH43 showed in the opposite way(P<0.05).In the ARDB analysis,the resistant types in the control group were 57,and the probiotic 58 with methicillin added,while in the antibiotic group,the reistant type reached to 61,one multiple drug resistance gene with resistance to monobactam,ceftazidime and cephalosporin_iii were emerged in the E_coli.These results showed that the Bacillus amyloliquefaciens TL and aureomycin mediated cecum microbiota showed an increased ability to nutrient metabolism such as glyceride,linoleic acid and nondigestible carbonhydrates such as acetylxylan,cellobiose,and the ability to hazardous substance degradation such as bisphenol and Styrene,which indicated that the use of Bacillus amyloliquefaciens TL and aureomycin could enhance the feed efficiency,but the use of aureomycin induced the emergence of the multiple drug resistance gene with resistance to monobactam,ceftazidime and cephalosporin_iii,which put the health of chicken into risk. |
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