Presently, there is academic discussion as to whether domestic dogs are omnivores or carnivores. The classification in the Order Carnivora does not necessarily mean that a dog's diet must be restricted to meat. Unlike an obligate carnivore, such as a cat, a dog is not dependent on meat protein in order to fulfill its dietary requirements. Dogs are able to healthily digest a variety of foods including vegetables and grains, and in fact can consume a large proportion of these in their diet. Wild canines not only eat available plants to obtain key amino acids, but may also obtain nutrients from vegetable matter from the stomach contents of their herbivorous prey. Domestic dogs can survive healthily on a reasonable and carefully designed vegetarian diet, particularly if eggs and milk products are included. Some sources suggest that a dog fed on a stict vegetarian diet may develop dilated cardiomyopathy since it lacks L-carnitine.[3]
In the wild these diets are typically pursued in the absence of available meat. It has also been noted that extremely stressful conditions, such as the Iditarod race and scientific studies of similar conditions, suggest that high-protein diets including meat help prevent damage to muscle tissue. This research is also true of other mammals.
Dogs sometimes eat grass, a harmless activity. Explanations abound, but rationales such as that it neutralizes acid are just guesses. Eating grass might make the dog vomit, so one explanation is that dogs eat grass to remove unwanted content from their stomachs.