At least the chickens, if they're kept in a somewhat natural way, have the chance to enrich their diet with worms and stuff, whether the human owners want them to or not?!? I mean, trying to keep them from digging seems pretty hopeless. (And the kind of person who keeps birds in wire cages is not likely to care about the vegan-ness of their food.) I've seen vegan cat food, too, which is just sick. Poor kittens. Also: poor human kids with vegan parents. Humans are clearly not made to thrive that way, either, and while a wholeheartedly support an adult's freedom to put their morals over their own health, kids can't make that decision yet.