What is the song old major sings to the animals at the end of chapter one in the book animal farm by George Orwell?

He says it is horrible. The animals labor tirelessly for the humans in exchange for a meager amount of food. The animals are forced to give up their young, and are inevitably killed before they reach a mature age. Horses are whipped, pigs are bred to be killed for pork and bacon, and cows milk is taken to feed humans. With the exception of Old Major, the animals have lived miserable lives under the Dictatorship of the farmer, Mr. Jones. Old Major calls upon the animals, telling them that a revolution will happen soon and change the horrible state they live in.