Although the propaganda says that all animals are equal, clearly the pigs and, to some extent, the dogs that work for them are "more equal." Some inequalities are seen right off.
As soon as the commandments are put up, it is noticed that all the milk is gone. We later find out the pigs are having it for themselves.
A second thing is that the pigs don't do any manual labor. They just tell the other animals what to do.
A third thing is that the pigs took over the harness room as their own private headquarters.
Finally, they are the only ones who get to study there -- only they get to study the important subjects.