This is an extremely controversial topic and one which even divides most vegans. Surely it's both cruel and unnatural to force a meat-free diet onto a canine - surely they absolutely need meat in order to be healthy? The answer is in fact very simple even though the issue seems so complicated, contentious and divisive.
If you're a vegan - and as such, a true animal lover - it's likely that you share your home with companion animals, and that you have found it to be a difficult moral situation when buying food for them. What is the point of boycotting products which involve cruelty or killing – only to adopt a dog or two and then provide them with foods which involve cruelty and killing? You are saving up to two hundred animals per year by living vegan, but then negating this positive by paying towards the torture and deaths of possibly hundreds more. The products that are found in store-bought pet food come from the bleakest, most brutal depths of animal agriculture. Even worse; often the meat found in cheap supermarket cans comes from the hundreds of thousands of dogs who are euthanized in shelters around the country each year.
On a brighter note...luckily, dogs (unlike cats) are not obligate carnivores. Dogs can live healthily and happily on a meat-free diet, and studies have shown these dogs to have a far longer lifespan when given the correct nutrients, vitamins, and minerals. In fact, the longest recorded lifespan of a dog was Bramble the vegan dog, who lived to 25! Recent studies, such as those described here, found that pets raised only on store-bought pet foods were shown to suffer from long term "kidney, liver, heart, thyroid, neurologic, neuromuscular, skin, and infectious diseases, and bleeding disorders." Basically, the domestic dog is so far removed from its wolf ancestors, after thousands of years of domestication and human interaction, that most house dogs are about as similar to a wolf as you are to a capuchin monkey. Leave most domestic dogs out in the wild and they are more likely to go hunting for a human to play with and a comfy sofa to snuggle up on, than a prey animal to munch on.
Obviously, though, when making a big change to your dog’s diet, it is important to transition slowly and carefully, just as you would with your own food. Slowly switch over to a vegan dog kibble (there are plenty available, including Halo and V-Dog, and they all contain all of a dog's vital nutrients) and you can also add a scoop of homemade "wet" food. When I have time, I make batches and freeze them for the coming week, and if I don't have time that week I simply make a little extra human food at dinner time to add to his kibble – beans or lentils, brown rice, pasta, pumpkin or sweet potato (mixed up with peanut butter, obvs!) are favourites. If you cannot access vegan kibble or would prefer not to, I would recommend adding a supplement such as VegeDog - so ensure your pup is getting absolutely all of the nutrients and minerals that he needs.
It comes down to this: if your lifestyle is based on the notion of avoiding all suffering to animals then, of course, this should extend to all of the products which you buy, to the best of your ability. There's plenty of information, resources and fun recipes out there for you to research - check out the links below and happy feeding!