A Utopia is a perfect society. Explain why animal farm can appropriately be called anti-utopian fiction

Animal Farm is a dystopian allegory. The story started as an animal utopia but became an animal dystopia by the end. Certainly old Major's vision of all animal's sharing the wealth was apparent at the beginning. The pigs or intelligencia got a taste of power. They twisted Old Major's message into a self-serving ideology. From there Napoleon twisted it further to quench his never ending ambitions. There are course many details in between but that's the general idea.