Effects of Yeast Products on the Apparent Total Tract Macronutrient Digestibility, Oxidative Stress Markers, Skin Measures, and Fecal Characteristics and Microbiota Populations of Healthy Adult Dogs

Brewer's yeast has high nutritional value and contains bioactive compounds that may promote health. Functionalized canola meal (FCM) is a high-fiber ingredient that has been proposed as a carrier for brewer's yeast. The objective of this experiment was to determine the apparent total tract digestibility (ATTD) of diets containing yeast-enriched FCM and test their effects on the fecal characteristics and microbiota, skin measures, and serum oxidative stress markers of adult dogs. Twelve dogs were fed four extruded kibble diets (control (no FCM or yeast), FCM + low yeast dose, FCM + medium yeast dose, and FCM + high yeast dose) in a replicated 4x4 LSD. Dogs fed yeast-enriched FCM had greater wet fecal output (~15% greater than control). The ATTD of DM, OM, and fat was lower in the diets containing FCM, although the values remained >80% for all macronutrients. The yeast-enriched FCM altered the relative abundance of a few bacterial genera (<i>Eubacterium brachy</i>, <i>Peptoclostridium</i>, <i>Ruminococcus gnavus</i>) and fecal phenol and indole concentrations. Other fecal characteristics, metabolites, bacterial diversity indices, skin measures, or oxidative stress markers were not affected. These findings suggest that yeast-enriched FCM can be incorporated into canine diets without compromising stool quality or nutrient digestibility and may affect microbial metabolism.