In vitro versus in situ evaluation of xylan hydrolysis into xylo-oligosaccharides in broiler chicken gastrointestinal tract

Xylan hydrolysis into xylo-oligosaccharides (XOS) was evaluated both in the gizzard and ileum of broiler chickens, and by a 2-step in vitro digestion assay that simulated the pH, temperature and time period of the gastric and small intestine (SI) phases. Twelve dietary treatments with varying soluble and insoluble xylan levels, either with or without supplemental xylanase, were fed to broiler chickens (n=576) for the in situ analysis, and were exposed to the in vitro assay. Relatedness of the two methods was strong for determination of XOS production in all dietary treatments for X₅, X₄, X₃, X₂ and X₁, respectively, in both the gastric (r=0.980, 0.853, 0.894, 0.870 and 0.951) and small intestine phase (r=0.957, 0.923, 0.940, 0.970, 0.969) (P<0.05). Consequently, the in vitro assay was used to illustrated the diversity of XOS production across different batches of wheat and barley in the presence of xylanase.