Not all of the animals on the farm, depicted in George Orwell's novel Animal Farm, are equal.
This idea is supported given the fact that it is one pig (Old Major), alone, who puts the idea of rebellion into the minds of the other animals. After Old Major's death, two other pigs (Snowball and Napoleon) take charge and lead the other animals into rebellion.
This idea is also corroborated through by the fact that not all of the animals can read and the rules of the farm need to be condensed to only one rule: "Four legs good, two legs bad."
Throughout the novel, different animals show different loyalties and possess different titles (like Snowball being named as the Animal Hero). In the end, Snowball is chased off of the farm and Napoleon is named the leader.
Therefore, all of the animals possess different labels according to ability. Much like the human world, many of the animals are considered equals.