In vitro fermentation of selected fibrous substrates by dog and cat fecal inoculum: influence of diet composition on substrate organic matter disappearance and short-chain fatty acid production.

Two in vitro fermentation experiments were conducted to evaluate the influence of source of dietary fiber fed to dogs and cats on fermentative activity of their fecal microflora. In Exp. 1, six English Pointer dogs were fed a diet containing either a non-fermentable fiber (Solka Floc) or a fermentable fiber (citrus pulp). A fecal sample from each dog was used as the inoculum source to determine in vitro OM disappearance (OMD) and short-chain fatty acid (SCFA) production from selected fibrous substrates. When data were pooled across substrates and fermentation times, a lower (P = .02) OMD (24.8 vs 29.4%) and a higher (P = .01; 3.8 vs 2.2) acetate to propionate ratio (A:P) occurred for the Solka Floc than for the citrus pulp diet. In Exp. 2, six short-hair cats were fed a diet containing no supplemental fiber (NF) or a diet containing beet pulp (BP). When data were pooled across substrates and fermentation times, NF resulted in a greater (P < .01) A:P than the BP diet (3.4 vs 1.5). The BP treatment resulted in a slightly higher (P = .07) OMD (42.0 vs 39.3%) and a higher (P = .07) propionate production (.74 vs .47 mmol/g of OM) than the NF diet. In summary, in vitro substrate OMD increased and A:P decreased when fecal inoculum from dogs and cats fed diets containing a supplemental source of fermentable fiber was used. In vitro fermentation of fibrous substrates by fecal microflora from dogs and cats increased with inclusion of fermentable fiber in the diet.