Cows have four stomachs. Often when a calf is born the farmer will make it swallow a magnet. This is to attract the various nails, staples, tacks, bits of wire, and so on that the cow may ingest while grazing. (This odd hunger is known to farmers as “hardware disease”) When the animal is slaughtered, the butcher will remove the magnet along with the metallic debris and sell the mass of iron and steel for scrap.