Dietary fiber for dogs: IV. In vitro fermentation of selected fiber sources by dog fecal inoculum and in vivo digestion and metabolism of fiber-supplemented diets

Two experiments were conducted to evaluate single sources and blends of dietary fiber in dog food. In Exp. 1, 14 fibrous substrates were fermented in vitro using dog feces as the source of inoculum. Organic matter disappearance was lowest (P < .05; < 10%) for Solka Floc and oat fiber and greatest (P < .05; > 80%) for fructooligosaccharides (FOS) and lactulose. Solka Floc, oat fiber, gum karaya, and xanthan gum produced the least (P < .05; < 1 mmol/g of substrate OM) total short-chain fatty acids (SCFA). Lactulose, citrus pectin, and guar gum produced the greatest (P < .05; > 6.8 mmol/g of substrate OM) total SCFA. In Exp. 2, six diets were formulated based on results obtained in Exp. 1. Treatments included 1) beet pulp (BP), 2) Solka Floc (SF), 3) citrus pulp (CP), 4) stool blend (SB), 5) SCFA blend (SC), and 6) combination blend (CB). Digestibility of DM and total dietary fiber (TDF) was greatest (P < .05; 87.3 and 60.8%, respectively) for dogs consuming the SC diet. Feces from dogs fed SC were scored as more unformed and liquid in consistency than feces from dogs fed the other diets. Dogs consuming the SF and SB diets had the lowest (P < .05; 11.0 and 4.1%, respectively) TDF digestibilities. Organic matter disappearance values derived from substrates fermented in vitro reasonably predicted the fiber digestibility of diets fed to dogs. Moderately fermentable dietary fiber sources, such as BP, promote excellent stool characteristics without compromising nutrient digestibility, and may promote gastrointestinal tract health by optimizing SCFA production.