Effects Of Lactobacillus Reuteri LR1 On The Growth Performance,intestinal Barrier Function And Amino Acid Transportation In Weaned Piglets

This study was conducted to investigate the effects of Lactobacillus reuteri LR1,a new strain isolated from the feces of weaned piglets on growth performance,intestinal morphology,immune responses,intestinal barrier function and amino acid transportation in weaned piglets.In the first part:Focus on the effect of LR1 on the growth performance of weaned piglets.A total of 144 Duroc×Landrace×Yorkshire weaned piglets?21 d of age,initial BW=6.49±0.02 kg?were randomly assigned to 3 dietary treatments with 8 replicate pens,each of treatment and 6 piglets.Piglets were fed a basal diet?CON,control?,the basal diet supplemented with 100 mg/kg olaquindox and 75 mg/kg aureomycin?OA,antibiotics?or the basal diet supplemented with 5×10¹⁰ cfu/kg L.reuteri LR1?LR1?for a 14-d period.Average daily gain?ADG?,Average daily feed intake?ADFI?and ratio of feed to gain?F:G?were calculated respectively.The results showed that,the ADG of piglets supplemeted with L.reuteri increased?22.73%,P<0.05?compared with control group,ADG?29.63%,P<0.05?and ADFI?17.82%,P<0.05?of antibiotics fed pigs were similar to those of L.reuteri fed piglets.There were no differences in diarrhea incidences and F:G among groups?P>0.05?.In the second part:At the end of the trial,1 randomly selected piglet from each pen was euthanized for sample collection for the investigation of the effects of L.reuteri LR1 on intestinal morphology,immune responses and intestinal barrier function in weaned piglets.The results showed,1)the villus height of the ileum was increased?P<0.05?and crypt depth in jejunum was reduced?P<0.05?,along with increased?P<0.05?villus height to crypt depth ratio of the jejunum and ileum by L.reuteri LR1 compared with control and antibiotics groups.2)L.reuteri LR1 increased?P<0.05?ileal mucosal content of transporming growth factor-??TGF-??and had tendency to increase IL-22?P=0.056?compared with antibiotic group.Compared with control group,L.reuteri LR1 increased?P<0.05?the mRNA abundance of porcine beta-defensin 2?pBD2?and protegrin 1-5?PG1-5?in both jejunal and ileal mucosa.Antibiotic decreased?P<0.05?the jejunal content of secretory immunoglobulin A?sIgA?,and mRNA abundance of pBD2 and PG1-5 in ileal mucosa.3)Compared with control group,L.reuteri LR1 increased?P<0.05?tight junction protein zonula occludens-1?ZO-1?and occludin transcripts in the mucosa of the jejunum and ileum,and those of MUC-2 in ileal mucosa.Additionally,L.reuteri LR1 decreased the activity of serum diamine oxidase?DAO?in weaned piglets?P<0.05?.4)L.reuteri increased?P<0.05?mRNA expression of toll-like receptor 2?TLR2?and TLR4 in jejunal mucosa and decreased?P<0.05?expression of TLR4 in ileal mucosa compared with control group.In the third part:At the end of the trial,1 randomly selected piglet from each pen was euthanized for sample collection to further investigate the effects of L.reuteri LR1 on intestinal amino acid transportation and mTORC1 signaling pathway in phaseI piglets.The results showed,1)no significant alterration of serum,jejunal and ileal mucosa free essential amino acids concentrations were observed in both L.reuteri LR1 and antibiotics supplemeted piglets?P>0.05?,but concentrations of jejunal mucosal urea and serum 3-MeHis were decreased?P<0.05?in L.reuteri LR1 supplemented piglets,compared with control groups.2)Compared with control group,LR1-fed piglets had higher?P<0.05?mRNA expression levels of ATB^0,+,CAT1,xCT,SNAT2,SLC38A9 in duodenal mucosa,ASCT2,4F2hc,ATB^0,+,b^0,+AT,xCT,SLC38A9 in jejunal mucosa,and rBAT,B⁰AT1,IMINO,SLC38A9 ileal mucosa.While OA increased?P<0.05?mRNA expression levels of b^0,+AT in duodenal mucosa,ASCT2,rBAT,CAT1,CAT2 in jejunal mucosa,and CAT1,CAT2,SLC38A9 ileal mucosa.3)Compared with control group,piglets fed L.reuteri LR1 had higher?P<0.05?protein abundances of Akt,p-S6 in jejunal mucosa and p-mTOR,Akt,p70S6K,p-S6 in ileal mucosa.Antibiotics-administrated piglets had higher?P<0.05?jejunal mucosal protein abundances of Akt,p-Akt,4EBP1,p-4EBP1and ileal mucosal p-mTOR,p70S6K,p-4EBP1 than those of control group piglets.The calculated p-Akt/Akt ratio was lower?P<0.05?but p-S6/S6 ratio was higher?P<0.05?in jejunal mucosa of L.reuteri LR1 fed pigs than those of control group,and ratio of p-4EBP1/4EBP1 of ileal mucosa in antibiotics group was increased?P<0.05?compared with control group.In conclusion,these data indicated that dietary L.reuteri LR1 supplemention at 5×10¹⁰cfu/kg improved of growth performance,intestinal morphology and intestinal barrier function,and promoted amino acid transportation and absorption and protein synthesis in the intestine.L.reuteri LR1 may be considered as an effective alternative to antibiotics for pig production.