Effects Of Bacillus Subtilis On Caecal Microflora And TLRs Expression In Chick

The study was aimed to investigate the effects of Bacillus subtilis(BS)on gut microflora diversity digestive enzyme activity and expression of Toll-like receptors(TLRs)in chick.A total of 240,1-day-old?817?crossbred broiler chickens were randomly allocated into 4groups with 3 replicates.The four groups were control group(basal diet,BD),group?(BD with 300 g/d BS,1.08×10~7CFU/kg),group?(BD with 600 g/d BS,2.16×10~7CFU/kg),and group?(BD with 900 g/d BS,3.24×10~7CFU/kg).Samples were collected at the 21st day.Results:Compared with control group,the difference of?diversity and?diversity between control group and treatment groups were not significant,but the abundance of some microorganisms in the treatment groups were improved,and the core microorganisms were different detween groups.Furthermore,the abundances of Lactobacillus of treatment groups were improved.Compared with the control group,the protease activity in ileum of experimental groups was significantly increased(p<0.05).Protease activity in ileum of group?and?was improved by 22.95%(p<0.01)and14.49%(p<0.05).The amylase activity in ileum of treatment groups was significantly increased(p<0.05).Amylase activity of group?and?were no significant difference,but that of group?was increased by 41.86%(p<0.01).Compared to control group,expression of TLR1A and TLR7 in the jejunum and caecum of treatment groups were significantly up-regulated.And expressions of them in ileum were decreased.The expression of TLR1B gene was significantly improved in the ileum,and significantly down-regulated in the cecum.Transcription levels of TLR2A and My D88 in jejunum,liver,spleen and kidney were significantly increased,but their expression was significantly lower in the ileum and cecum.TLR2B expression in jejunum and caecum was significantly lower.Expression of TLR3 in jejunum,ileum,cecum,liver and spleen were significantly increased.Expression of TLR4 gene in the jejunum and ileum were significantly upregulated.TLR15transcription levels in the jejunum and caecum were obviously improved.TLR15transcription levels in jejunum,liver,and spleen were significantly improved.Furthermore,TLR15 expressions in kidney of group?and group?were significantly higher than controls.Transcription level of TLR21 in the jejunum ileum and cecum was significantly downregulated.IL-1?experession in spleen and kidney were significantly increased.Conclusion:B.subtilis could not regulate the caecal microflora diversity,but improved amount of some gut probiotics such as lactobacillus,the digestive enzyme activity,regulate the some immunogene exprssions and enhance the immune capacity of animal.