In Animal Farm, what does Napoleon mean when he says "but any animal that absented himself would have his rations reduced by half"?

This quote can be found at the beginning of Chapter Six. This chapter picks up at a point when the experiment on the farm is beginning to go a bit sour. Snowball has just been driven from the farm, leaving Napoleon basically unchallenged in his rule. The animals are exerting themselves more and more in the construction of the windmill (which was Snowball's idea, though Napoleon has now taken credit for it). The animals, we learn, are working "like slaves," and Napoleon adds to their sixty-hour a week workload by announcing that there will be a workday on Sunday as well. While work is "voluntary," the animals will have their "rations reduced by half." This refers to their food rations, and therefore means that the work is not really "voluntary": if they refuse to work on Sundays, they will starve. Aside from showing how Napoleon, like other dictators, consolidates his power by perverting the ideals of the society, this passage demonstrates an important theme in Animal Farm--the manipulation of language in service of power. By saying that extra work on Sundays is "voluntary," Napoleon keeps the facade of democracy on the farm. But in reality, as we have seen, it is hardly voluntary. It is an exercise in arbitrary power by a pig who is becoming increasingly despotic and abusive of his authority.