At the end of the book, the pigs have set themselves up as surrogate humans. They run the farm, taking advantage of the hard work of the other animals to live in a comfortable, decadent lifestyle. The other animals toil without much benefit to themselves, and the pigs exploit them far more than Jones ever did. When the other farmers come to visit, intending to create an alliance with the pigs, they are contemptuous of the working animals:
"If you have your lower animals to contend with," he said, "we have our lower classes!" This bon mot set the table in a roar; and Mr. Pilkington once again congratulated the pigs on the low rations, the long working hours, and the general absence of pampering which he had observed on Animal Farm.
(Orwell, Animal Farm, msxnet.org)
The farmers, who are prosperous, look down on their workers as much as they look down on the animals. After all, they are able to live in comfort due to the hard work of the "lower classes," meaning their employees and other workers, and so they have no need to treat them as equals. While the Animal Farm originated as a way to ensure equality, it becomes clear that the eventual fate is no better than the classist system that existed in human society.