How xylanase alters arabinoxylan utilisation in broilers; characterization of the in vivo formation of arabinoxylanoligosaccharides

The objective of the presented study was to extract and identify the arabinoxylanoligosaccharides (AXOS) released in vivo in the different segments of the gastro-intestinal tract (GIT) of broilers and demonstrate the influence of xylanase on arabinoxylan (AX) utilization. The study used samples from digesta collected from the gizzard, ileum, ceca and excreta of broilers, fed wheat-soybean meal diet without (CTL diet) or with xylanase supplementation (ENZ diet).

Molecular weight (Mw) distribution analysis was performed with purified (A)XOS by HPSEC-RI and oligomers present were profiled by HPAEC-PAD. Different HPSEC profile for ENZ compared to CTL were shown. CTL diets mainly presented molecules between 10-100 kDa Mw, while smaller molecules between 10-1 kDa Mw were more abundant for ENZ. This shift in size distribution was aligned with AXOS presence for ENZ.

The in vivo AXOS profile matched the one obtained during in vitro hydrolysis of soluble wheat AX by the same xylanase. This supports that AXOS detected for ENZ were formed by the supplemented xylanase. AXOS were also detected in excreta for ENZ, and presented similar profile to the ileum. The in vivo formation of AXOS is in line with the AX depolymerization and with AX solubilization from the water-extractable cell wall matrix. Additionally, AXOS formation in the upper GIT may further explain the positive influence of xylanase supplementation on ceca fermentation processes (Singh et al., 2021). As previously documented (Kouzounis et al., 2021; Singh et al., 2021), the release of (A)XOS in the upper GIT was correlated with pronounced cecal fermentation. In the current study, soluble compounds with Mw < 10 kDa were present in the ceca, however, AXOS were not present, suggesting that extensive fermentation, of AX species, has occurred in the ceca.

Using a recently developed HILIC-MSn methodology, formed AXOS were identified; AXOS with degree of polymerization (DP) 4-10 were present in ileum and excreta samples of birds fed ENZ diet, which aligned with improved AX utilization in the hindgut.

In this study, xylanase supplementation of broiler diets resulted in AXOS formation in vivo. The detection and characterization of released oligosaccharides further delineated the impact of dietary xylanase on hindgut fermentation in broilers. In particular, it is proposed that low-substituted AXOS and XOS, released in vivo by the xylanase, were extensively fermented by the ceca microbiota. Our work highlights the contribution of dietary xylanase to animal health and provides valuable insight on the utilization of AX and AXOS along the GIT of broilers.