Is it morally permissible for a Lion to kill a Zebra for food ? Of course it is ! They ' re animals , and they evolved to kill other animals for food . But , WE ' re also animals , and killed animals for food over all of our evolution , and have a physiology designed to digest animals . We cannot live by Kale alone . Why should Our kind of animal be more constrained to depart from its nature , than any other kind of animal ? Because We have understanding , and they don ' t , you answer . AHA ! And there ' s the answer to the original question as well . Pigs have no understanding of mortality . They surely understand pain and suffering , but not death . If we can kill them in such a way as to avoid suffering , we ' ve done them no harm . I wouldn ' t want to kill an elephant , since they appear to understand death , mourn their dead , etc . If we didn ' t eat pigs , there would be many fewer of them in the world . Over 95 % of the weight of the mammalian biome consists of domesticated animals , mainly raised for food . If we didn ' t eat them , the vast majority of pigs , cows , chickens , etc wouldn ' t exist at all . We give them life , protect them from disease and predators that would kill them much more painfully than we do or should do . Would morality require that we raise them all , at considerable expense , but keep them as pets and not eat them ?