The process of making chicken feed: whole grains are ground up, and the amendments are added. This is mash. Mash is then moistened, and extruded into pellet form, and dried. These are pellets. The pellets are then crushed up a bit. This is crumble. Mash should be the cheapest, followed by pellets, with crumble requiring the most processing, therefore most expensive. If you are fermenting your feed, and can get mash, go for that. It should be cheaper. When ever you buy feed, look at the nutritional analysis and the mill date first, then look at the form of the feed last (if feeding FF)