When the animals force Farmer Jones from the farm, they first celebrate, and then the pigs lead them to work, since the harvest must be brought in for winter. At the time, the animals are all elated, and happily labor under the idea that the fruits of all work will be shared equally.
...the implements had been designed for human beings and not for animals, and it was a great drawback that no animal was able to use any tool that involved standing on his hind legs. But the pigs were so clever that they could think of a way round every difficulty.
(Orwell, Animal Farm, george-orwell.com)
Naturally, the farm equipment is not designed to be operated by animals, but the pigs, showing their intelligence and propensity for delegating work, figure out ways for the animals to work while taking a "leadership" role themselves. While the other animals provide great effort in actually harvesting the crops, the pigs "supervise," allowing them to benefit from the work of others while performing minimal labor themselves.