摘要Since the caecal microbiota of young broilers are not yet able to ferment the dietary fibre(DF)fraction of the feed to a large extent,increasing the accessibility of DF substrates along the gastrointestinal tract is crucial to benefit from the health stimulating metabolic end-products(e.g.butyric acid)generated upon microbial DF fermentation.Therefore,the present study aimed to evaluate the potential of reduced-particle size wheat bran(RPS-WB)and endoxylanases as feed additives to stimulate arabinoxylan(AX)hydrolysis and fermentation along the hindgut of young broilers.To this end,RPS-WB and endoxylanase supplementation were evaluated in a 2×2 factorial design using a total of 256 male 1-d-old chicks(Ross 308).Broilers were assigned to 4 dietary treatments:a basal wheat-based diet with(1)no feed additives(control,CTRL),(2)an endoxylanase(XYL;Econase XT 25 at 0.10 g/kg diet),(3)1％wheat bran with an average reduced particle size of 297 μm(RPS-WB)and(4)an endoxylanase and 1％RPS-WB(RPS-WB+XYL).Each dietary treatment was replicated 8 times and on d 10 and 28,respectively,24 and 16 broilers per treatment group were euthanised to analyse AX degradation,short-chain fatty acid pro-duction and digesta viscosity in the ileum and caecum.Broilers receiving XYL in their diet showed increased AX solubilisation and fermentation at both d 10 and 28 compared to the CTRL group(P＜0.05).Adding RPS-WB to the diet stimulated wheat AX utilisation by the primary AX degraders in the caecum at 10 d of age compared to the CTRL group,as observed by the high AX digestibility coefficient for the RPS-WB supplemented group at this young age(P＜0.05).At 28 d,RPS-WB supplementation lowered body-weight gains but increased butyric acid concentrations compared to the XYL and CTRL group(P＜0.05).Although no synergistic effect for RPS-WB+XYL broilers was observed for AX hydrolysis and fermentation,these findings suggest that both additives can raise a dual benefit to the broiler as a butyrogenic effect and improved AX fermentation along the ileum and caecum were observed throughout the broiler's life.