I've just read something about people keeping cats on a vegan diet and it makes me so, so angry. Because you can't without abusing and endangering your cat. They are obligate carnivores, their physiology is not capable of processing plant matter efficiently and need special nutrients only found in animal sources and will get ill or die without them. Taurine, essential vitamins (like A & B1), fatty acids for example and their digestive tract is built for meat not plants. If you don't want a carnivorous animal, don't get a cat. If you can't accept that, don't get ANY kind of pet except for a plushie