In vitro study on the role of endoxylanase-driven fibre solubilisation and fibre particle size in improving fibre fermentation in broilers.

Endoxylanases are commonly used in broiler production, but a better understanding of their role in stimulating fibre fermentation can improve the associated performance and health benefits. Combining particle-size-reduced bran with endoxylanase can increase fibre accessibility for microbial fermentation, but it is unclear if this is driven by the precaecal fibre solubilisation by endoxylanase or by its action within the caecal lobes. Endoxylanase action was studied under simulated ileal and caecal conditions using different wheat bran particle sizes. First, the effects of bran particle size (29 to 1312 µm), pH and endoxylanase (Econase XT 25, 1 mg/g bran, 160,000 BXU/kg bran) on fibre solubilisation were evaluated under ileal in vitro conditions. Endoxylanase addition and bran particle size reduction increased water-extractable arabinoxylan (WE-AX) content during incubations between pH 4 and 8 (P < 0.050). WE-AX content also increased with decreasing bran size without endoxylanase (P < 0.001). Next, the effect of bran size (coarse, 1312 µm, and fine, 134 µm) and endoxylanase treatment (pretreatment-added, fermentation-added, no addition) on fermentation was studied through an in vitro fermentation using broiler caecal inoculum. The endoxylanase-pretreatment of bran resulted in a rapid early fermentation, while the fermentation-added endoxylanase resulted in the highest gas and volatile fatty acid (VFA) production, but only after 24 h (P < 0.050). Fine bran tended to increase gas production (P = 0.062) and linear VFA production (P = 0.041) after 6 h, while it increased branched-chain VFA production after 24 h (P = 0.026). The combination of endoxylanase and particle-size-reduced bran increased gas production and lactic acid content after 6 h (P < 0.050). The addition of endoxylanase during the pretreatment and directly to the fermentation elicited distinct fermentation responses, although both actions seem to benefit fibre fermentation in a fermentation-time-dependent way. These results indicate that endoxylanase activity may be important in both ileal and caecal conditions to improve fibre fermentation in different ways, potentially enhancing gut health and broiler performance in vivo as well.