Chaff is also made by chopping straw (or sometimes coarse hay) into very short lengths, using a machine called a chaff cutter. Like grain chaff this is used as animal feed, and is a way of turning coarse fodder into a form more palatable to livestock.he process of loosening the chaff from the grain so as to remove it is called threshing â traditionally done by milling or pounding. Separating remaining loose chaff from the grain is called winnowing â traditionally done by repeatedly tossing the grain up into a light wind which gradually blows the lighter chaff away.