Minecraft wiki entry for Animal_farming, associated text: The chickens in the room with the hopper floor will start laying eggs when they grow up and the eggs will be transported through the hoppers and into the dispenser, which will fire them onto the slab. Some of the eggs will hatch and the baby chickens are not tall enough, even while standing on the slab, to get burnt by the lava that is directly above their heads. However, when they grow up, they are too tall and their heads go straight into the lava. The chickens die and since they burn to death their meat becomes cooked. All of the feathers and chicken that they dropped gets sucked up by the hopper under the slab and deposited into the chest below the hopper.