摘要Background It is important to promote intestinal development and maturation of chicks for feed digestion and uti-lization,intestinal health,and disease resistance.This study aimed to investigate the effects of dietary yeast cell wall polysaccharides(YCWP)addition on intestinal development and maturation of chickens and its potential action mechanism.Methods 180 one-day-old male Arbor Acres broilers were randomly assigned to three groups containing control(basal diets without any antibiotics or anticoccidial drug),bacitracin methylene disalicylate(BMD)-treated group(50 mg/kg)and YCWP-supplemented group(100 mg/kg).Results Compared with control group,in-feed antibiotic BMD continuous administration significantly decreased crypt depth(d 21)and villus height(d 42)along with mucosal maltase activity(d 42)in the ileum(P＜0.05).Also,BMD markedly downregulated gene expression levels of β-catenin,lysozyme,occludin and FABP-2(d 21)and innate immune related genes CD83 and MHC-Ⅰ mRNA levels(d 42,P＜0.05),and decreased goblet cell counts in the ileum of chickens(d 21 and d 42,P＜0.05).While,TLR-2,TLR-6 and iNOS mRNA abundances were notably upregulated by BMD treatment(d 42,P＜0.05).Nevertheless,dietary YCWP addition significantly increased the ratio of villus height to crypt depth(d 21),villus surface area(d 21 and d 42),ileal alkaline phosphatase and maltase activities as well as goblet cell(d 21 and d 42)and IgA-producing plasma cell numbers as compared to BMD treatment(d 21,P＜0.05).YCWP addition also upregulated gene expression levels of Lgr5,Wnt/β-catenin signaling pathway related gene(Wnt3,β-catenin,d 21;β-catenin,d 42),intestinal cells proliferation marker Ki-67 and barrier function related genes(occludin,d 21 and d 42,P＜0.05).Moreover,YCWP significantly increased antigen presenting cell marker related genes(MHC-Ⅱ,d 21;CD83 and MHC-Ⅰ,d 42),TLR-1,TLR-2 and TLR-6 mRNA levels(d 21,P＜0.05).Cecal microbiome analysis showed that YCWP addition obviously improved cecal microbial composition,as indicated by increasing relative abundance of Fournierella,Psychrobacter and Ruminiclostridium on d 21,and Alistipes and Lactobacillus on d 42,which were posi-tively related with gut development and maturation related indexes(P＜0.05).Conclusion Collectively,YCWP promoted yet antibiotic BMD delayed intestinal morphological and immunological development linked with modulating gut microbiome in chickens.