Effects Of Dietary Fiber And Essential Oils Supplementation On Growth Performance And Intestinal Health In Weaned Piglets Challenged With Enterotoxigenic Escherichia Coli

Dietary fiber and essential oils,as the components of natural plants,have attracted the attention of many researchers for the advantages of safety,environmentally friendly and wide sources.However,the application effects of dietary fiber and essential oils were unstable in pig production,the effect of a single use was limited,and the application of dietary fiber in combination with essential oils has rarely been reported.Accordingly,the present study was to evaluate the effects of dietary fiber（inulin and microcrystalline cellulose）and essential oils(Mix Oil^?)supplementation on the growth performance of weaned piglets under a normal condition,and whether they alleviate the effects on growth performance,immune function and intestinal health of weaned piglets after the enterotoxigenic Escherichia coli（ETEC）challenge.Forty-two Duroc×Landrace×Yorkshire crossbred weaned piglets（28±1 d age）with similar body weight（7.92±0.43 kg）were randomly allotted to one of six dietary treatments with 7 replicates per treatment and one piglet per replicate.The dietary treatments were,（1）non-challenged control（CON;pigs fed a basal diet and orally infused with the sterile saline）;（2）ETEC-challenged control（ETEC;pigs fed a basal diet and infused with ETEC）;（3）ETEC challenge+antibiotics（AT;pigs fed a basal diet with 75 mg/kg chlortetracycline+25 mg/kg virginiamycin+50 mg/kg quinocetone and orally infused with ETEC）;（4）ETEC challenge+mixed dietary fiber（MDF;pigs fed a basal diet with 0.5%soluble fiber inulin+0.5%insoluble dietary fiber microcrystalline cellulose and orally infused with ETEC）;（5）ETEC challenge+mixed essential oils(MEO;pigs fed a basal diet with 200 mg/kg Mix Oil^?and orally infused with ETEC);（6）ETEC challenge+MDF+MEO(MDF+MEO;pigs fed a basal diet with 0.5%soluble fiber inulin+0.5%insoluble dietary fiber microcrystalline cellulose+200 mg/kg Mix Oil^?and orally infused with ETEC).The test was divided into two parts,normal test（21 d）and challenge test（4 d）,and the trial lasted 25 days.On day 22,piglets with weight per kg in the challenged treatments（ETEC,MDF,MEO,MDF+MEO）were orally administered 10 mL of sterile saline containing approximately 6×10⁹CFU/mL ETEC,and piglets in the non-challenged control treatment（CON）were orally administered an equal volume of sterile saline.On day 26,all piglets were anesthetized and slaughtered.During the days 1～21（pre-challenge）（1）Compared with CON group,MDF+MEO group improved（P<0.05）ADFI and ADG of piglets,and the other groups（AT,MDF,MEO）also improved the growth performance in different degrees（P>0.05）.Meanwhile,MDF and MEO group decreased（P<0.05）the diarrhea incidence of piglets,but AT group was the opposite（P<0.05）.When compared with AT group,the diarrhea incidence of piglets in other groups（AT,MDF,MEO or MDF+MEO）was significantly reduced（P<0.05）.Additionally,MEO had a higher（P<0.05）ATTD of CP.（2）Compared with CON group,MDF addition increased（P<0.05）serum IgA,IL-4and IL-10 concentration,MEO increased（P<0.05）serum IgA concentrations and decreased（P<0.05）serum IL-6 and TNF-αconcentrations,MDF+MEO reduced（P<0.05）serum IL-6 and TNF-αconcentrations.Meanwhile,all treatments（AT,MDF,MEO and MDF+MEO）improved（P<0.05）serum T-AOC and GSH-Px activity.During the days 22～25（post-challenge）（1）Compared with CON group,ETEC challenge significantly decreased（P<0.05）ADG and tended to reduce（P=0.056）ADFI,and increased（P<0.05）the diarrhea incidence and tended to increase（P=0.087）diarrhea index.Compared with ETEC group,AT and MEO supplementation improved（P<0.05）ADG,and all treatments（AT,MDF,MEO and MDF+MEO）relieved（P<0.05）the diarrhea incidence.MDF and MEO group also significantly decreased（P<0.05）the diarrhea incidence when compared to AT group.（2）Compared with CON group,ETEC challenge markedly decreased（P<0.05）serum IgA and IL-4 levels,improved（P<0.05）serum IL-1βand TNF-αlevel,and tended to increase（P=0.051）serum IL-6 level.Compared with ETEC group,MDF and MDF+MEO had a higher（P<0.05）serum IL-4 level,MEO inhibited（P<0.05）the reduction of serum IgM and IL-4 level.And no difference（P>0.05）was observed on serum immunoglobulins and cytokines between AT and ETEC group.（3）Compared with CON group,ETEC challenge increased（P<0.05）MDA concentrations in serum and jejunal mucosa of piglets,and tended to decrease（P=0.064）serum T-AOC.Compared with ETEC group,MDF and MDF+MEO had a higher（P<0.05）serum T-AOC,MEO inhibited（P<0.05）the reduction of serum T-AOC and T-SOD activity,MDF+MEO relieved（P<0.05）the enhancing of MDA concentrations in serum and jejunal mucosa of piglets.（4）Compared with CON group,ETEC challenge decreased（P<0.05）the mRNA abundance of AQP3 in jejunal mucosa of piglets.Compared with ETEC group,MDF up-regulated（P<0.05）mRNA expressions of AQP3,AQP8,MEO and MDF+MEO increased（P<0.05）mRNA expression of AQP1 and AQP3,respectively.Furthermore,ETEC induced a higher（P<0.05）serumLPS concentration and DAO activity of piglets.However,MDF and MDF+MEO inhibited（P<0.05）the enhancing of serumLPS concentrations and DAO activity,MEO decreased（P<0.05）the serumLPS concentrations after ETEC challenge.（5）Compared with CON group,ETEC infection down-regulated（P<0.05）mRNA levels of ZO-1,Occludin and MUC1,and tended to decrease（P=0.088）mRNA abundance of Claudin-1 in jejunal mucosa.MDF and MEO inhibited（P<0.05）the ETEC-induced down-regulation of Claudin-1 and ZO-1 mRNA expression,respectively,and MDF+MEO inhibited（P<0.05）the ETEC-induced down-regulation of Claudin-1 and Occludin mRNA expression in jejunal mucosa.Additionally,the relative mRNA abundance of MUC1 in jejunal mucosa of piglets with AT,MDF and MDF+MEO was up-regulated compared to CON group（P<0.05）.（6）Compared with CON group,ETEC challenge increased（P<0.05）IL-4,IL-6,IL-10,IL-1βand s IgA concentrations and the relative mRNA abundance of IL-6 in the jejunal mucosa.When compared to ETEC,MEO group had a lower（P<0.05）IL-6 mRNA expression in jejunal mucosa,MDF+MEO was observed to decrease（P<0.05）IL-4,IL-6,IL-10,TNF-αconcentrations and the IL-6 mRNA expression,AT markedly increased（P<0.05）the IL-1βmRNA expression in the jejunal mucosa of piglets.Furthermore,ETEC challenge increased（P<0.05）the relative mRNA abundance of IRAK1and NF-κBp65,and tended to increase（P=0.083）the TLR4 mRNA expression in the jejunal mucosa of piglets.However,MEO inhibited（P<0.05）the enhancing of NF-κBp65 mRNA expression,MDF+MEO inhibited（P<0.05）the increase of TLR4,TRAF6 and NF-κBp65 mRNA expression,but AT group markedly increased（P<0.05）the CD14 and My D88 mRNA expression after ETEC challenge.（7）Compared with CON group,ETEC infection up-regulated（P<0.05）the populations of Escherichia coli in colonic digesta,and down-regulated（P<0.05）the populations of total bacteria,Bifidobacterium in cecal digesta and total bacteria,Lactobacillus in colonic digesta.When compared to ETEC,MDF increased（P<0.05）cecal total bacteria,Bacillus,Bifidobacterium populations and colonic total bacteria populations.MEO diet inhibited（P<0.05）the increase of Escherichia coli populations and the reduction of total bacteria populations in cecal and colonic digesta,but AT decreased（P<0.05）the populations of Bifidobacterium in colonic digesta of piglets after ETEC challenge.Meanwhile,lower（P<0.05）butyric acid concentrations in cecal digesta,lower（P<0.05）total SCFAs and butyric acid concentrations in colonic digesta were observed after piglets challenged with ETEC.Meanwhile,ETEC infection tended to decrease the cecal total SCFAs（P=0.072）,colonic acetic acid（P=0.070）and propionic acid（P=0.083）concentrations of piglets.Correspondingly,higher（P<0.05）pH value was observed in colonic digesta of ETEC group when compared with CON.However,MDF supplementation prevented（P<0.05）the reduction of total SCFAs,acetic acid,propionic acid and butyric acid concentrations in colon.MEO inhibited（P<0.05）the reduce of total SCFAs and propionic acid concentrations in cecum induced by ETEC.In summary,mixed fibers,essential oils and the combination of the both improved the growth performance by enhancing the immune function and antioxidant capacity of weaned piglets under a normal condition.The combination of mixed fibers and essential oils had the best effect on the promotion of growth performance,which was better effect than that of antibiotics.ETEC challenge resulted in the decrease of growth performance and the increase of diarrhea via decreasing immune function,antioxidant capacity,disturbing intestinal flora and impairing the intestinal barrier function of piglets.However,mixed fibers,essential oils and the combination of the both could effectively protect piglets from ETEC-induced injury on a certain extent.Essential oils had the best protection,included alleviating the inhibition of growth performance,decreasing diarrhea,enhancing immune function and antioxidant capacity,regulating the intestinal flora structure,promoting the production of SCFAs,and improving intestinal barrier function.