Arabinoxylan Enhances Intestinal Mucosal Barrier Function and Antioxidant Capacity in Suckling Piglet Associated with Remodeled Gut Microbiota and Upregulated AHR-Related Signaling

Milk replacers are essential when breastfeeding is limited, but strategies for incorporating functional polysaccharides to support neonatal intestinal development remain unclear. Here, suckling piglets were used as a model to investigate the effects of arabinoxylan (AX) supplementation in a milk replacer on growth, intestinal function, and microbiota-related metabolism. Piglets received a milk replacer containing 0%, 1%, 2%, or 3% AX. AX improved growth in a dose-responsive manner, with 2% AX showing the greatest benefit. Compared with the control group, 2% AX increased ether extract digestibility and jejunal and ileal villus height and jejunal goblet cell abundance. AX also enhanced tight junction protein and MUC2 expression, improved the antioxidant capacity, and reduced jejunal MDA accumulation. Microbiota and metabolomic analyses showed that AX reshaped the colonic microbial composition and altered tryptophan metabolism, accompanied by changes in intestinal AHR-related signaling and enhanced jejunal Nrf2-related responses, including increased nuclear Nrf2 abundance and Nrf2 nuclear localization. These findings support AX as a promising fiber-based ingredient for functional milk-replacers.