Answer: Yes. (But great care and attention is required.)
That's the good news for any vegan or vegetarian who wants to ensure a beloved pup gets the nutrition it needs. It's also good news for those who are just really interested in eating ethically, and object to the ingredients in many dog foods, which can contain slaughterhouse offal (byproducts of cattle, pigs, chicken, and lamb) or other meats that you'd never touch.
But that's not to suggest there's no debate on the subject: Some veterinarians still worry that a meatless diet -- usually made from some combination of soybean meal, mashed vegetables, and synthetic vitamins and minerals -- may not be an adequate substitute for one with meat. And when we contacted the American Veterinary Medicine Association, the leading organization of vets, a representative wrote to tell us that "the Association doesn't have a policy on this issue."
The AVMA did recommend we speak with Amy Farcas, a clinical veterinary nutritionist at the University of Pennsylvania, who told us that it's less important wherethe specific ingredients of a dog's diet come from, and more important that they contain the right amount of nutrients -- like amino acids, vitamins, mineral, and fatty acids. "Dogs are omnivores, which means they have a pretty adaptable [gastrointestinal] tract, and that their nutritional needs can be met through different means," she said. We should point out that the most definitive research on the subject, a 2006 National Research Council report, by a team of animal nutrition experts from universities around the world, supported this theory, claiming a vegetarian diet is healthy for dogs as long as it's balanced, particularly with enough protein and vitamin D. (Another 2009 study from the University of New England studied the effects of a plant-based diet on dogs that exercise a lot-- namely, sprint-racing Siberian huskies -- and showed no negative health effects.)