Metabolic profiles show few differences in serum amino acid, one-carbon and fatty acid compounds in dogs fed a plant-based ('vegan') or meat-based diet

Sarah Dodd^1*Jennifer L Adolphe²Anna Katharine Shoveller³Cate Dewey⁴Deep Khosa⁴David Ma⁵Sarah K Abood⁴Adronie Verbrugghe^1*

• ¹Ontario Veterinary College, University of Guelph, Guelph, Canada
• ²University of Saskatchewan Department of Veterinary Biomedical Sciences, Saskatoon, Canada
• ³University of Guelph Department of Animal Biosciences, Guelph, Canada
• ⁴University of Guelph Ontario Veterinary College, Guelph, Canada
• ⁵University of Guelph Department of Human Health and Nutritional Sciences, Guelph, Canada

Dogs are omnivores, not herbivores, and yet entirely plant-based diets are formulated to meet their current known nutrient recommendations. However, little is known about the metabolic effects of feeding diets containing no animal-derived nutrients. Metabolomics allows for the investigation of dietary influences on animal metabolism and physiology beyond what may be revealed by routine healthcare assessments. This study compared serum metabolomics in a longitudinal trial including 61 healthy adult dogs fed an experimental extruded plant-based ('vegan') diet (PLANT, n=31) or a commercial extruded meat-based diet (MEAT, n=30) for 3 months. Both diets met industry nutrient recommendations for maintenance of adult dogs and had similar levels of total protein and fat, though amino acid and fatty acid profiles differed. Free amino acid and protein, one-carbon, carbohydrate, fatty acids and lipid metabolites were analysed at the start and end of the trial. Organic acids and lipid metabolites were measured using direct injection liquid chromatography tandem mass spectrometry, one carbon and folate pathway metabolites by liquid chromatography-multiple reaction monitoring mass spectrometry, and fatty acids by gas chromatography. Repeated measures mixed modelling assessed metabolite differences between diet groups over time. Eleven of 47 amino acid and protein metabolites, 0 of 16 carbohydrate metabolites, 3 of 29 one-carbon/folate pathway metabolites, 21 of 61 fatty acids and 27 of 78 lipid metabolites differed between diets. Dogs maintained on PLANT demonstrated few changes associated with sulfur amino acid metabolism, but unexpectedly showed a reduction in the serum branched-chain amino acids (BCAA) isoleucine, and valine despite higher dietary provision, though no differences in BCAA ketoacids were found. A reduction in serum creatinine without corresponding changes in creatine was also observed in the PLANT group, along with a lower total serum FA and omega-6 to omega-3 FA ratio, despite higher fat content