Effects Of Viable And Heat-killed Enterococcus Faecium On Intestinal Microbiota Structure And Immune Response In Suckling Piglets

The purpose of this study is to compare the effects of viable and heat-killed Enterococcus faecium on the gut microbiota structure and immune response in suckling piglets and on immune response in small intestinal epithelial cells in pigs,which provide the basis for clarifying the mechanism that regulate the intestinal health of piglets by viable and heat-killed Enterococcus faecium.The main findings are as follows:Experiment 1.Nine litters newborn piglets[crossbred(Large White×Landrace)× Duroc]were randomly divided into three groups:control group,viable bacteria group and heat-killed bacteria group(three litters per group).From birth to 6-days-old,each group was orally administered with 10%skimmed milk 10 mL piglet-1 day-1,with 10%skimmed milk containing viable Enterococcus faecium 10 mL piglet-1 day-1(1×10~8 CFU/mL)and with 10%skimmed milk containing heat-killed Enterococcus faecium(1×10~8 CFU/mL)10 mL piglet-1 day-1,respectively.The mucosa of the jejunum and ileum and the contents of the ileum and colon were separately collected at 7-and 21-days-old for analyzing the intestinal microbiota and the expression of mucosal cytokine genes.The results showed that both the viable and heat-killing Enterococcus faecium significantly reduced the relative abundance of the genus Lactobacillus in the ileal microbiota of piglets(21 days old)(P=0.03),significantly decreased the relative abundance of the genus Bacteroides in the colonic microbiota of piglets(7 days old)(P=0.03)and significantly increased the relative abundance of the phylum Proteobacterial in the colonic microbiota of piglets(21 days old)(P=0.05).The viable and heat-killing Enterococcus faecium had basically similar effects on the other phyla and genera of intestinal microbiota in the piglets,but they were all not significant.Experiment 2.The IPEC-1 cell experiment was set up to control group,viable bacteria group and heat-killed bacteria group containing PBS,viable bacteria(1×10~8 CFU/mL)and heat-killed bacteria respectively,with 6 repetitions in per group.Then they were co-incubated with the IPEC-1 cells for 1 h and 3 h,and were collected.The results showed that viable Enterococcus faecium significantly increased the secretion of IL-8 in the jejunum mucosa to piglets(21-days-old)(P<0.05).Heat-killed Enterococcus faecium significantly increased the expression level of IL-8 gene in jejunum mucosa of piglets(21 days old)(P<0.05).Both the viable and heat-killing Enterococcus faecium significantly increased the expression level of TNF-a gene in ileum mucosa of piglets(21 days old)(P<0.05)?Both viable and heat-killed Enterococcus faecium significantly increased the expression levels of IL-8,TNF-a,and TGF-?in IPEC-1 cells at 1 and 3 h(P<0.05).In addition,there were significant difference in the expression levels of IL-8(3h)and TNF-a(1h)genes between viable E.faecium and heat-killed E.faecium(P<0.05).However,the viable and heat-killing Enterococcus faecium significantly reduced the IL-10(3h)gene expression level(P<0.05).In summary,it is generally consistent that the effect of viable and heat-killing Enterococcus faecium on the ileal and colonic microbiota of suckling piglets,and on the cytokine immune response of small intestinal mucosa in piglets and IPEC-1 cells.