In vitro models of the canine digestive tract as an alternative to in vivo assays: Advances and current challenges.

Dogs occupy a full place in the family and their well-being is of paramount importance to their owners. Digestion, a complex process involving physicochemical, mechanical, and microbial parameters, plays a central in maintaining animals healthy. As in vivo studies in dogs are more and more restricted by ethical, regulatory, societal, and cost reasons, an alternative option resides in the use of in vitro models simulating the different parts of the canine gastrointestinal tract. This review paper first introduces digestion and gut microbiota as key factors in dog nutrition and health, under both healthy and diseased conditions (obesity and inflammatory bowel disease), by highlighting when relevant similarities or differences between human and canine digestion process. Then, we provide for the first time an in-depth description of currently available models of the canine digestive tract, discuss technical and scientific challenges that need to be addressed and introduce potential applications of in vitro gut models in food and veterinary fields. Even if the development of some in vitro models remains limited by a lack of in vivo data in dogs necessary for a relevant configuration and validation, translation of long-term expertise on human in vitro gut models to dog’s ecosystem opens avenues for canine in vitro gut model development and their adaptation to specific digestive conditions associated to various ages, sizes, breeds and/or diets, under both physiological and diseased states.