The Community Structure And Functional Genes Of The Chicken Gut Microorganism And The Chicken Growth

Global chicken production is important to human food security.Sub-therapeutic antibiotics have long been used as growth promoters in chicken farming;however,the resulting antibiotic resistance threatens public health.Macleaya cordata extract(MCE),a safe and natural growth promoter derived from plant,with effective ingredients of benzylisoquinoline alkaloids,is a competitive alternative to antibiotics in poultry industry.Although the mechanisms of growth promoters are still not fully understood,it is known that the altered intestinal microbiota plays important roles.To better understand the mechanisms of growth promoters and the regulated gut microbiota,we developed a DNA extraction method from bacterial samples of the chicken gastrointestinal tract,and constructed the first comprehensive chicken gut microbial gene catalog.Then,we identified the distinctive characteristics and temporal changes in the foregut and hindgut microbiota.Finally,we performed the parallel experiments on dietary supplementation of MCE and chlortetracycline(CTC),in comparison.Chickens feed with MCE and CTC had improved growth performance.Major impacts on the intestinal microbiota were confined to the foregut.The predominant genus in the foregut,Lactobacillus,was enhanced by MCE.Meanwhile,the biosynthesis pathways for amino acids,vitamins,and secondary bile acids were also significantly enriched.In comparison,CTC increased the antibiotic-producing bacteria of Kitasatospora and Streptomyces,which are also multi-antibiotic resistant bacteria.The microbial synthesis pathways of antibiotics,fatty acid,unsaturated fatty acid and secondary bile acid were enhanced.These findings provide insight into the foregut microbiota and unveiled the different mechanisms of growth promoters.Noteworthy,we found the sub-therapeutic CTC accumulated antibiotic-resistant genes(ARGs)in the foregut,which increased the risk of ARGs dissemination into the environment and pathogens.Therefore,it once again underscores the importance and urgency of developing effective and safe natural growth promoters.