In Vitro Fermentation Characteristics of Dietary Fibers Using Fecal Inoculum from Dogs Consuming a Dried Brewers Yeast Product

The increasing demand for functional ingredients has drawn attention to yeast and yeast-derived ingredients in pet foods. This experiment aimed to evaluate the in vitro fermentation characteristics of common dietary fibers using fecal inoculum from dogs fed either a control diet (CTRL) or a diet supplemented with dried brewers yeast at 1.5% inclusion (BY). Sixteen healthy adult dogs were acclimated for 7 d and then randomly assigned to the two treatments (<i>n</i> = 8/group) for 21 d. Fecal samples collected at the end of the treatment period, were preserved in 20% glycerol and later used as inoculum for in vitro fermentation of beet pulp, pectin, and cellulose over 0, 6, 12, or 18 h. Fermentation patterns differed among fiber substrates. Pectin was highly fermentable, beet pulp showed moderate fermentation, and cellulose was minimally fermented, as indicated by SCFA production and pH changes. Within each fiber, BY inocula produced more SCFA and a lower pH than CTRL after 18 h, with the largest SCFA differences observed in beet pulp tubes (3549 vs. 2980 μmole/g) and the greatest pH differences in pectin tubes (-1.66 vs. -1.54). Microbiota analysis revealed increased relative abundances of SCFA-producing genera, along with reduced relative abundances of <i>Fusobacterium</i>, <i>Streptococcus</i>, and <i>Sutterella</i>. Overall, dried brewers yeast supplementation can influence canine gastrointestinal microbiota composition and fermentative activity in vitro.