Glucose-based oligosaccharides exhibit different in vitro fermentation patterns and affect in vivo apparent nutrient digestibility and microbial populations in dogs

To evaluate the potential of indigestible oligosaccharides (OS) to serve as "dietary fiber-like" ingredients, it is necessary to determine their extent of indigestibility. In vitro fermentation characteristics of two novel OS, alpha-glucooligosaccharides (GOS) and a maltodextrin-like OS (MD), were compared to those of fructooligosaccharides (FOS), gum arabic (GA), guar gum (GG) and guar hydrolysate (GH). Total short-chain fatty acid (SCFA) production (mu mol/g dry matter) as a result of MD fermentation was higher initially compared with GA (P < 0.01), but GA was more extensively fermented at 24 h (P < 0.01). Total SOFA production for GOS was similar to that for FOS, GG, GH and GA. In the second experiment, GOS and MD were added at 6% to an enteral formula control diet (Control) and fed to ileal-cannulated dogs in a 3 x 3 replicated Latin-square design. Ileal digestibility of glucose was lower (P < 0.05) and carbohydrate (CHO) numerically lower (P = 0.08) for both GOS and MD compared with the Control, Total tract digestibility of CHO and glucose was lower only for MD (P < 0.01) compared with the Control. Total fecal weights were higher (P < 0.01) for both GOS and MD treatments. Fecal concentration of bifidobacteria was numerically increased by GOS and MD supplementation (P = 0.13 and 0.23, respectively). Thus, GOS and MD are indigestible yet fermentable OS, and may act as "dietary fiber-like" ingredients.