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 role in maintaining canine health. As in vivo studies in dogs are increasingly restricted by ethical, regulatory, societal, and cost pressures, an alternative option is the use of in vitro models simulating the different compartments of the canine gastrointestinal tract. This review introduces digestion and gut microbiota as key factors in dog nutrition and health under both healthy and diseased conditions (obesity and inflammatory bowel disease) and highlights similarities and differences between the human and canine digestive tract and processes. We provide the first 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 the food and veterinary fields. Even if the development of some in vitro models is still limited by a lack of in vivo data in dogs that is necessary for relevant configuration and validation, translation of long-term expertise on human in vitro gut models to dogs opens avenues for model optimization and adaptation to specific canine digestive conditions associated with various dog ages, sizes, breeds and/or diets, in both physiological and diseased states.