Protection Of Chitooligosaccharides On Intestinal Inflammation Piglets Challenged By ETEC

Intestinal inflammation,as one of the most common diseases in livestock and poultry production,not only endangers animal health,reduces animal welfare,harms the economic interests of farmers but also puts tremendous pressure on environmental protection.Chitooligosaccharides(COS)has important physiological activities such as antibacterial,antioxidant,anti-inflammatory and neuroprotective,so that it can play a role in improving growth performance,improving animal intestinal health,improving body immunity and antioxidant properties,etc.,which makes COS have the potential to be an antibiotics-alternative feed additive.The purpose of this experiment is to study the effects of diet supplementation with COS on production performance,blood routine,intestinal morphology,intestinal microbes and signaling pathways IL-6/JAK/STAT3 and TGF-β1/STAT5/FOXP3 related to Th17/Treg balance in intestinal inflammation piglets induced by ETEC.The experiment adopted a 2×2 factorial design,and the main factors were COS(with or without COS in the basic diet)and ETEC challenge(with or without ETEC challenge).32healthy,28-day-old Duroc×(Landrace×Yorkshire)(DLY)three-way weaned boars with similar parity and weight range of 6.72±0.40 kg were selected and randomly divided into 4treatments and each treatment is comprised of eight piglets:(1)CON,piglets fed basal diet and orally administered with liquid medium;(2)ETEC,piglets fed basal diet and orally challenged with 10 m L 1.0×10~9CFU/m L ETEC bacterial solution;(3)COS,piglets fed COS diet and orally administered with liquid medium;(4)COS*ETEC,piglets fed basal diet with500 mg/kg COS and orally challenged with 10 m L 1.0×10~9CFU/m L ETEC bacterial solution.The results showed:(1)Growth performance and blood routine:ETEC challenge reduced piglet ADG,kidney coefficient and spleen coefficient greatly significantly(P<0.01),significantly improved piglet F/G,diarrhea frequency,and diarrhea index(P<0.05),COS significantly increased piglet ADG,ADFI,kidney coefficient,and spleen coefficient(P<0.05),significantly reduced piglet F/G and the percentage of peripheral blood neutrophils(P<0.05),and decreased piglet peripheral blood neutrophils trend of absolute value(P=0.060),COS reduced the F/G of piglets challenged by ETEC(P<0.05);ETEC increased the peripheral blood neutrophils,eosinophils and HGB of piglets(P<0.05),and decreased the absolute value of peripheral blood neutrophils,eosinophils and the percentage of neutrophils in piglets(P<0.05).COS alleviated the increase in the absolute value of eosinophils in the peripheral blood of piglets caused by ETEC challenge(P<0.05).The results showed that ETEC caused intestinal inflammation in piglets and reduced piglet production performance and organ index,and led to the infiltration of peripheral blood inflammatory cells;COS helped to improve piglet’s growth performance,organ index and blood routine index;COS reduced the adverse effects of piglet growth performance and blood routine indicators attacked by ETEC(2)Intestinal morphology and intestinal flora:ETEC challenge increased the crypt depth of piglets and the histopathological score of the piglet’s ileum(P<0.05),and COS increased the pile height and the PH/CD of piglets(P<0.05),COS had no significant interaction effect on the deterioration of intestinal morphology caused by ETEC(P>0.05).ETEC challenge significantly increased the depth of piglet crypts and piglet ileal disease histopathological score(P<0.01),tended to reduce the abundance of Streptococcus(P=0.082)and Rumenococcus UCG-002(P=0.069).COS significantly increases Chao1,Shannon,Observed OTUs,and the abundance of Bacteroides and Prevotella(P<0.05),significantly reduced the abundance of Firmicutes,Lactobacillus,Streptococcus,Muribaculaceae＿unclassified,and Anarovovrio(P≤0.05),tended to increase the abundance of Prevotella＿9(P=0.086),Prevotella(P=0.094)and Phascolarctobacterium(P=0.091).COS inhibited the increase in the abundance of Streptococcusof piglets caused by ETEC challenge(P<0.05).The results showed that:ETEC induced intestinal inflammation in piglets,which worsens the intestinal morphology and intestinal flora structure of piglets.COS effectively promoted the development of piglet intestinal villi,increased the species diversity of piglet’s intestinal flora and the abundance of beneficial bacteria,and inhibited the proliferation of piglet’s intestinal pathogenic bacteria.COS inhibited the abundance of pathogenic bacteria in piglets with intestinal inflammation.(3)Intestinal immunity and protein expression of inflammatory factors in serum:ETEC induced intestinal inflammation in piglets,which significantly increased the relative abundance of IL-6,IL-21,STAT3 and RORc m RNA in the intestinal mucosa of piglets(P<0.05),and significantly reduced the relative abundance of IL-10 and FOXP3 m RNA in the intestinal mucosa of piglets.COS significantly reduced the relative abundance of IL-10,STAT3 and FOXP3 m RNA in the intestinal mucosa of piglets(P<0.05),tended to reduce the relative abundance of TGF-β(P=0.080),STAT3(P=0.091)and STAT5(P=0.061)m RNA in the intestinal mucosa of piglets.COS inhibited the increase in the relative expression abundance of STAT3 m RNA in the ileal mucosa of piglets caused by ETEC challenge(P<0.05);COS and ETEC challenge had no significant effect on the protein expression of IL-1β,IL-6,IL-17A,IL-17F,IL-21,IL-22 and TGF-β1(P>0.05),the two had no significant interaction effect on the protein expression of these cytokines(P>0.05).The results show that intestinal inflammation activated the IL-6/JAK/STAT3 signaling pathway in the piglet’s intestinal mucosa and inhibited the TGF-β1/STAT5/FOXP3 signaling pathway.Promote the differentiation of Th17 cells and the secretion of pro-inflammatory factors,hindered the differentiation of Treg cells and the secretion of anti-inflammatory cytokines;COS inhibited the activation of the IL-6/JAK/STAT3 and TGF-β1/STAT5/FOXP3 signaling pathways in the intestinal mucosa of piglets;COS protected the ileal mucosa of piglets with intestinal inflammation mainly through the IL-6/JAK/STAT3 signaling pathway.In summary,this study shows that ETEC challenge can lead to diarrhea and inflammation in piglets,and be used to construct the E.coli-induced piglet intestinal inflammation model;COS can improve the growth performance of piglets,relieve the infiltration of inflammatory cells in the peripheral blood of piglets,promote intestinal development,optimize the structure of piglet intestinal flora,promote digestion and metabolism of piglets and reduce the risk of disease in piglets;COS has a protective effect on piglets with intestinal inflammation induced by ETEC challenge in terms of growth performance,blood routine indicators,intestinal microbial homeostasis and Th17/Treg cell imbalance.