When I adopted my cat he was a vegan. His old owner fed him vegan canned food. I, of course, got him a tin of cat food at the first store we came to. He wolfed down the whole thing and then puked all over my cat carrier. Over the next month he learned to love real cat food. He also jumped off a table and shattered both his hip bones due to malnutrition. See he had been a vegan since kitten hood and had massively demineralized bones. He lived 12 years after that but his kidneys gave out. They think early due to his early malnutrition
See, this bothers me.
If you're vegan, and you want a vegan pet, get a rabbit or guinea pig, or something else herbivorous or at least omnivorous. Cats CANNOT survive on a vegan diet, their digestive systems simply are not designed to process plant matter properly.
I understand if you are making a moral choice to ensure no animals are harmed due to your eating habits, but your pets don't eat based on moral choices, they eat based on what nature designed their biology for. If you're saving the animals by not eating them, then starving your own pet by trying to force it to be an herbivore when evolution says otherwise, you are batting in the karmic negatives.