For dogs, actually eater and vegetarian diets is done, however they have to be done very, very rigorously. there's plenty of area for error, and these diets in all probability don't seem to be as applicable as diets that contain a minimum of some animal macromolecule.
Dogs and cats cannot create fat-soluble vitamin in their skin, thus it has to be in their diet. and also the fat-soluble vitamin has to be D3, that comes from animal sources, not D2, that comes from plant-based sources. “People and dogs will use D2 to some extent, however cats really want D3,