Even though it can be done, I would not feed a veggie diet to cats. Unless you are prepared to test their urine for acidity levels every couple of weeks, I would not toy with it. Cats need acidic urine, and with certain added items (I think it's called VegCat), can achieve that, but it varies as to how much each cat needs. I know that's not what you wanted to hear, but I have seen too many people (with their hearts in the right place!), harm their cats as a result of feeding them a vegetarian diet. Veggie diets with cats are VERY tricky, and can take a turn for the worse quickly. Kidney failure and urinary blockages are common problems. I feed my kitties a raw meat diet. Sounds strange, yes, a vegan feeding raw meat, but it's the healthiest for them, being natural carnivores.
I'm a vegan and I feed my cat a raw meat diet as well. Cat's aren't really designed to be vegetarian. In fact, they don't derive their energy from carbohydrates the way humans do; they get their energy from pure protein and will start to break down muscle if they are not receiving enough. Cats do not have amylase (enzyme that helps to digest grains and other carbohydrates) in their saliva and have very little of it in their stomach and pancreas. They don't digest carbohydrates well, and too much can cause them to bloat or become obese. They don't produce their own taurine, which is an amino acid found in raw meat, and they need omega-3 fatty acids in their diet but cannot receive them from flax or hemp oil because they don't have the ability to convert alpha-linolenic into DHA and EPA. Cats need diets high in fat, as their livers metabolize dietary fat for energy. These are just some of the reasons why cats should not be fed a vegan diet, as they have different physiology from humans. I buy the meat from an organic, local farm that uses humane practices and does not ship because they don't mass-produce. It's the best I can do to feed my cat an appropriate diet while not supporting factory farms and abused livestock. I do not wish to offend anyone with this information. If someone out there has a happy, healthy vegan cat, that is awesome. I adore cats and read a lot about them. If you are interested, there is a great book called "The Natural Cat" by Anitra Frazier, and it talks about holistic care for cats, preventative "treatment" through diet rather than waiting until the cat is sick...much like Alicia's book advises for us humans! Anyway, that was quite long, but I wanted to give a thorough explanation about the raw meat feeding, as at first glance, it might seem appalling. Good luck!
Raw organic meat is the optimal choice for cats because of the live enzymes present as well as the nutrients that have not been destroyed by the cooking process. However, I understand that people, even non-vegans, can be squeamish or simply hesitant to feed such a diet. If you are averse to raw meat feeding because you do not wish to have any meat in the house or because you simply can't stomach the idea of raw meat, then organic canned food is your best bet. Dried food is one of the most unnatural foods for cats because it often contains excess carbohydrates (which cats don't really need) and is very low in moisture. Cats don't have a strong thirst mechanism and derive most of their moisture needs from food. Semi-moist cat food is usually loaded with preservatives and is still not very close to a species appropriate diet. My two canned foods of choice are PetGuard and Wellness; both use human-grade organic meat with no byproducts. I don't buy canned food often, as I feed my cat raw meat, but I don't believe they are so much more expensive than normal cans...perhaps between 1 and 2 dollars, depending on the size? The companies don't spend their money on advertising, so they can afford to keep prices relatively low. Adult cats only need to be fed twice a day, and one small to medium sized can does one day for my cat on the rare chance she is getting it. You can put the leftover canned food in a glass mason gar and stir in a few drops of hot water to warm it up. If you only feed canned food, my guess is that it would be between $8 and $14 a week. You can make one can last longer by mixing in an organic egg yolk to the portions, but that is probably unrealistic since most of you guys won't have eggs in the house...I don't. High quality canned is the second best thing to raw meat because it is supplemented with the vitamins and nutrients that we know to be important for cats.
I am probably starting to sound like the crazy cat lady here, but just to clarify: If you do not want to feed raw meat because of the expense, then you should know it's actually cheaper! The kind of meat that comes from small, organic, local farms can be pricey, but I buy a whole chicken and portion it off. One needn't remove bone or organs. Raw bones will not splinter, and chewing on bones is good for the cat's jaws and teeth. Cats need a balance of organs, bone, meat and fiber. The fiber can come from vegetable sources (my cat steals my food!). If you portion the chicken or other kind of meat into mason jars or pyrex bowls in one day servings and place those in the freezer, then you can take one out each night and place it in the fridge. It will be thawed in half a day to a day. This way, the meat stays fresh. Cats have a strong sense of smell and most likely will not eat meat that has gone bad. One chicken tends to last a week and a half to two weeks, which ends up being quite inexpensive in the long run. Regardless of whether you decide to try the vegan cat food, raw meat diet, or organic canned, twice a day is optimal, and you needn't leave food out between meals. In between those feedings, the cats' bodies undergo a "mini-fast" by processing the food and disposing of the waste. Leaving food out actually stimulates the cat's sense of smell and therefore her digestive system, and they eat despite not being hungry. If your cat is turning up her nose to something, try sprinkling some nutritional yeast, nori flakes, or tiny drops of shoyu on the food (perhaps the vegan canned needs a bit of nutritional yeast to make it more appetizing? ;) My cat doesn't care for nori or shoyu on her food, but she loves nutritional yeast, and it's good for them. Just a tip in case you have a picky eater. Alright, I'm done for now, I promise! ;)