No! The answer is in the evolution of cats and dogs and the divergence of their “evolutionary paths” some 30 million years ago.
Both are scientifically classified within the class Mammalia and within the order Carnivora. The divergence in evolution resulted in dogs becoming members of the Canoidea superfamily and cats becoming members of the Feloidea superfamily1.
The Canoidea includes species “with very diverse dietary habits”1 while Feloidea includes species that have evolved as “strict carnivores”.
There would seem to be some debate as to whether the dog is carnivorous. Incidentally species in the order Carnivora are not necessarily carnivorous. “Most species of Carnivora are, to some degree, omnivorous, except the Felidae (cats)”2.
Linda P Case in her book1 says that dogs are omnivorous while other authors say that they are carnivorous3. Dogs are said to be adaptable carnivores4.
It probably doesn’t matter. What matters is that the cat is a strict or obligate carnivore while the dog is more flexible.
The cat has stuck to the strictly carnivorous diet even in domestication (perhaps, however, in 1000 or more years time the domestic cat will be less strict about what it needs to eat?). This has resulted in specific physiological and metabolic adaptations. In other words the cat’s digestive tract and chemistry has evolved to accept animal tissue and almost nothing else. There are minor exceptions. Cats do eat grass and one big cat, the snow leopard deliberately eats vegetation to enhance its absorption of oxygen as it lives at high altitude.
The cat then has “peculiarities in nutritional requirements”1 while the dog is very adaptable and can survive on an omnivorous diet. The cat cannot survive on an omnivorous diet.
The cat’s dietary requirements are more stringent than that of the dog. The cat has a high protein requirement – too high for the dog on a long term basis. It has a need for taurine, arginine, arachidoonic acid and preformed vitamin A, for instance. See also Taurine Deficiency in Cats. Or how rice in cat food can affect taurine. Do Bengal cats need more taurine?
For a domestic cat, a diet without animal tissue would require supplementary additives to add in the required nutrients.
A dog eating cat food would find it too rich it is said and it might cause diarrhoea and obesity. One commentator said that a dog on a long term cat food diet might lose its eyesight5. I don’t know if this is true.
Dogs like the taste of cat food because it is rich in protein (higher protein content than dog food5) but can dogs eat cat food? Yes in small doses and occasionally but NO as a long term diet.
Can Dogs Eat Cat Food? – Notes:
1. The Cat, Its Behavior, Nutrition & Health by Linda P Case.