Why do the hens protest Napoleon's decision to sell the eggs and how many hens die in their protest?

As there is need for more grain, Napoleon has Mr. Whymper arrange a contract to sell four hundred eggs per week. The hens rebel by laying their eggs in the rafters so that the eggs smash on the floor. Napoleon stops the hens’ rations and makes feeding a hen punishable by death. Nine hens die, supposedly of coccidiosis, during the five-day strike, after which the hens surrender.