Why were animals having to look like slaves?

The animals worked like slaves.... they didn't so much look like slaves. Napoleon made the animals work like slaves, but there was a method to his cruelty. If he worked them to exhaustion, they wouldn't have time to think about what they were doing, or how they were being treated. Thus, they wouldn't have the foresight to rise against him.

All that year the animals worked like slaves. But they were happy in their work; they grudged no effort or sacrifice, well aware that everything that they did was for the benefit of themselves and those of their kind who would come after them, and not for a pack of idle, thieving human beings.