As the animals build a third windmill, Boxer, their strongest horse, loses his strength because of old age and collapses. Napoleon sends him to be slaughtered, even though Boxer was his friend. The pigs continue to work with humans and start to behave like them, such as living in the farmhouse and walking on two legs. They teach the sheep a new chant: “Four legs good, two legs better”. The commandments are replaced by the words "All animals are equal, but some animals are more equal than others." In the end, other animals watch the pigs talking with a group of humans and decide they cannot tell which is which.