Gastrointestinal tract (GIT) infections are a major health problem accounting for a large percentage of veterinary admissions. Evidence suggests that probiotics, prebiotics, and synbiotics can be used to enhance the composition and activities of the colonic microbiota. Companion animal research lags humans but is increasing, focusing on various fibres as prebiotics in the companion animal GIT. Vickers et al. tested prebiotic fermentability, comparing yeast cell wall (YCW) with common fibre sources used in pet diets. Primary outcomes included bacterial growth as measured by fluorescence in situ hybridization (FISH) and short-chain fatty acids (SCFA) production after 10 and 24h of fermentation.