Apparent Total Tract Macronutrient Digestibility of Mildly-Cooked Human-Grade Vegan Dog Foods and Their Effects on the Blood Metabolites and Fecal Characteristics, Microbiota, and Metabolites of Adult Dogs.

Vegan, mildly-cooked, and human-grade dog foods are becoming more popular, as beliefs and views of pet owners change. To our knowledge, however, dog studies have not examined the digestibility of commercial vegan diets. Therefore, the objective of this study was to determine the apparent total tract digestibility (ATTD) of mildly-cooked human-grade vegan dog foods and their effects on blood metabolites and fecal microbiota, characteristics, and metabolites of adult dogs consuming them. Three commercial dog foods were tested. Two were mildly-cooked human-grade vegan dog diets, while the third was a chicken-based extruded dog diet. Twelve healthy adult female beagles (7.81±0.65 kg; 7.73±1.65 y) were used in a replicated 3x3 Latin Square design. The study consisted of three experimental periods, with each composed of a 7-day diet adaptation phase, 15 days of consuming 100% of the diet, a 5-day phase for fecal collection for ATTD measurement, and 1 day for blood collection for serum chemistry and hematology. During the fecal collection period, a fresh sample was collected for fecal scoring and dry matter, pH, metabolite, and microbiota measurements. All data were analyzed using the Mixed Models procedure of SAS (version 9.4). All three diets were shown to be highly digestible, with all macronutrients having digestibility values above 80%. The vegan diets had higher (P<0.001) ATTD of fat, but lower (P<0.05) ATTD of organic matter than the extruded diet. Dogs consuming the vegan diets had lower circulating cholesterol (P<0.001), triglyceride (P<0.001), and platelet (P<0.009) concentrations and lower (P<0.010) blood neutrophil percentages than dogs consuming the extruded diet. Dogs consuming vegan diets had lower (P<0.001) fecal dry matter percentages, lower (P<0.001) fecal phenol and indole concentrations, and higher (P=0.05) fecal short-chain fatty acid concentrations than those consuming the extruded diet. Fecal bacterial alpha and beta diversities were not different (P>0.05) among diets, but dogs consuming vegan diets had altered (P<0.05) relative abundances of nearly 20 bacterial genera when compared with those consuming the extruded diet. In conclusion, the mildly-cooked human-grade vegan dog foods tested in this study performed well, resulting in desirable fecal characteristics, ATTD, and serum chemistries. The vegan diets tested also led to positive changes to serum lipids and fecal metabolites, and interesting changes to the fecal microbial community.