By the end of Animal Farm, in chapter 10, the original Seven Commandments have been reduced to one, and this one has been changed from its original statement, "all animals are equal," to read "all animals are equal, but some animals are more equal than others."
Of course, it is logically impossible for some animals to be "more equal than others." Nevertheless, this has been the case, if not from the beginning of the animals taking over the farm, then from very soon after. Almost from the start, the pigs set themselves apart as the leaders and brainworkers and use this to justify extra privileges, such as eating the windfall apples themselves. This sense of privilege gradually gets worse and worse, especially after Snowball is run off the farm and Napoleon takes over, until, finally, the pigs live entirely separately and differently from the other animals. In fact, they live as human beings.