Well, as people go on saying nobody defends worms or fish but cats, there is a reason. Fish feel pain for about...5 seconds, then forget about said pain. Worms, more or less the same. Cat's feel pain, and constantly at that. It is cruel towards a cat, but a worm or fish, not as much. As for cows, humans mass produce cows for food, there isn't naturally millions and millions and millions of cows on earth. Not to mention, said mass produced cows are insta-killed, so they feel no pain. Not to mention, cows fart a lot thus ruin the ozone lair, so they simply must die.