Sequential Galacto- and Xylo-Oligosaccharide Feeding Transiently Modulates Gut Microbiota and Upregulates Intestinal Alkaline Phosphatase in Weaning Piglets

Improving growth and health at weaning remains a priority in pig production. This study investigates whether supplementation with galacto-oligosaccharides (GOSs) followed by xylo-oligosaccharides (XOSs) improves performance and gut health of healthy 28-day old weaning piglets. Pigs received either a control basal (CON) diet, the CON diet containing 1% GOS for 7 days followed by the CON diet containing 0.017% XOS for 47 days (GXOS), or the CON diet for 7 days followed by the CON diet containing 0.017% XOS for 47 days (XOS). Body weight, average daily gain, average daily feed intake, and feed conversion ratio did not differ between diets from day 1 of weaning (d1) to d54. At d7, GXOS pigs showed increased jejunal and caecal α-diversity (Shannon, inverse Simpson), distinct ileal β-diversity (Yu and Clayton, Bray-Curtis, Jaccard), and greater short-chain fatty acid-producing <i>Lactobacillus</i> and <i>Veillonella</i>; no taxa remained differentially abundant by d22, and the XOS group showed no microbiota shifts throughout the study. Jejunal goblet cell density was lower in GXOS pigs at d7. Jejunal and caecal <i>IL-1β</i>, <i>IL-6</i>, <i>IL-8</i>, and <i>IL-10</i> gene expression was transiently greater at d7 in GXOS pigs, whereas by d22 cytokine/chemokine differences resolved, whilst intestinal alkaline phosphatase was upregulated in the ileum and caecum (XOS) and colon (GXOS and XOS). Sequential prebiotic switching and delayed XOS onset likely missed the immediate post-weaning window, during which the gut microbiota is most receptive to dietary modulation, consequently limiting potential performance gains; therefore, prebiotic timing, sequence, and duration are critical to achieving functional benefits at weaning.