They were forced to forget that they were once human. They were pigs, being forced to lay in the mud, which was nice and warm at least. With their arms and legs bound, or with only stumps, all they were allowed to do was eat from the troughs, and fuck each other. Their offspring would become the new generation of pigs, raised with never knowing what it was like to be human, and never knowing how their parents were slaughtered for food.