I'm a lacto-ovo vegetarian, but my dog is a full-blown omnivore, who is fed a diet of rice, vegetables and fish daily. He seems to thrive on it, but the question I often get from other vegetarians is: "Why don't you make your dog go vegetarian?"
According to Pet MD, getting your dog to go vegetarian is not as harmful as doing the same to your cat. The same is said by veterinarians in this article as well, yet I do know people who continue to feed their cats vegetarian diets.
I'm all for vegetarian diets in humans, but animals are a different matter entirely, even dogs, who are omnivores. According to an article on Mother Nature Network, a vegetarian diet can be prescribed to dogs, provided it is nutritionally sound. However a vet quoted in the same article also says:
“Vegetarian proteins tend not to have all the amino acids, so you have to do multiple combinations of varying types of sources of protein to get the right amino acids, which can get a little tricky to manage,” says Dr. Jessica Waldman, a veterinarian who operates a full-time pet rehabilitation clinic in Santa Monica, Calif. Waldman says she steers her clients away from vegetarian diets because she believes they are unnatural.
“Although I think it would be possible to put a dog on a vegetarian diet, it is truly unnatural for them,” says Waldman. “There are still dogs in the wild and they eat a vast majority of animal protein, so I think that keeping your pet’s diet as close to natural is best for limiting disease and promoting health.”