| As a dietary supplement,Bacillus subtilis can improve the growth performance and immunity of animals,and also balance the intestinal bacterial and compete with pathogenic bacteria for colonization,thereby improving intestinal health.Dietary Bacillus subtilis has a good regulation effect on intestinal morphology,intestinal flora and immune system.Therefore,this study investigated the effects of Bacillus subtilis on intestinal health of growing-finishing pigs by analyzing intestinal barrier related indicators and microbial data.A total of 160 "Duroc × Landrace × Yorkshire" growing-finishing pigs with an average body weight of 36.82 ± 0.20 kg was randomly divided into 2 groups with 5 replicates per group.Bacillus subtilis(B.Subtilis)1000 mg/kg was added to the basal diet,and 2 samples(male and female)were collected from each repeat slaughter at the end of feeding period.In this study,the levels of immunoglobulin and cellular inflammatory factors secreted by intestinal mucosa,intestinal physical barrier and short-chain fatty acid receptor were detected,and the effects of Bacillus subtilis on intestinal barrier function and inflammatory signaling pathway of growing-finishing pigs were investigated by detecting intestinal inflammatory signaling pathway and mucin.The composition of microorganisms in colonic contents of growing-finishing pigs was detected by 16 S r RNA sequencing method,and the concentration and p H value of short-chain fatty acids in intestinal chyme were determined to investigate the effects of Bacillus subtilis on microbial and biological barrier function of colonic contents of growing-finishing pigs.The following results are obtained:1.Bacillus subtilis feed additive can improve intestinal morphology of growing-finishing pigs.The duodenum was stained with H&E and the intestinal morphology indexes were measured.Bacillus subtilis feed additive significantly increased villus height to crypt depth ratios(P<0.05)and significantly decreased crypt depth(P<0.05).2.Bacillus subtilis feed additive can improve intestinal physical barrier of growing-finishing pigs.Bacillus subtilis significantly increased tight junction protein m RNA expression levels(P<0.05),in addition,compared to the control group,B.subtilis significant elevated adhesive junction protein m RNA expression levels(P<0.01).Similarly,Bacillus subtilis significantly increased the expression levels of proteins related to duodenal physical barrier(P<0.05).3.Bacillus subtilis can improve the intestinal chemical barrier function of growing-finishing pigs.The results showed that the number of intestinal epithelial goblet cells in Bacillus subtilis group was higher than that in control group(P<0.01)and the MUC2 protein m RNA expression levels of was significantly elevated(P<0.01).In conclusion,Bacillus subtilis can improve the chemical barrier function of duodenum in growing-finishing pigs.4.Bacillus subtilis can improve the intestinal immune barrier function of growing-finishing pigs.Compared to the control group,the number of intestinal epithelial lymphocytes in Bacillus subtilis group was significantly increased(P<0.05).ELISA results showed that the content of TNF-α in duodenal mucosal inflammatory factors in Bacillus subtilis group was significantly decreased(P<0.05)and the concentration of IL-10 in Bacillus subtilis group were significantly higher(P<0.05).In addition,Bacillus subtilis significantly increased intestinal mucosal SIg A concentration(P<0.05).To further explore the mechanism of Bacillus subtilis improving intestinal barrier in growing-finishing pigs,we evaluated the expression levels of key molecules in inflammatory signaling pathways.Compared to control group,Bacillus subtilis significantly increased intestinal TLR2 m RNA expression level(P<0.05).In addition,Bacillus subtilis supplementation decreased the TLR4,My D88 and NF-κB m RNA expression levels in duodenum(P<0.05)and the NF-κB,TLR4,My D88 and TRAF6 protein expression levels in duodenum(P<0.05).These results suggest that Bacillus subtilis can enhance the intestinal immune barrier function,and that Bacillus subtilis can regulate the inflammatory response by inhibiting the inflammatory signaling pathway.5.Bacillus subtilis can improve the intestinal biological barrier function of growing-finishing pigs.High-throughput sequencing results showed that the addition of Bacillus subtilis increased the relative abundance of Firmicutes and Bacteroidetes(P<0.05).In addition,streptococcus and Clostridium were the dominant flora at the genus level.Compared with the control group,dietary Bacillus subtilis supplementation increased the relative abundance of unknown Clostridium(P<0.05).Meanwhile,the content of short-chain fatty acids in colon contents was determined,and dietary Bacillus subtilis supplementation significantly increased the concentration of short-chain fatty acids in colon contents(P<0.05).In addition,Bacillus subtilis significantly reduced the p H of colon contents(P<0.05). |
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