If you understand the steps to farming and agriculture, you realize that nothing is “left over.” Even if the farmer’s primary intent is to produce fruit or vegetables to eat or sell, he or she still uses the plant remnant itself to eventually fertilize the soil to produce more fruit and vegetables.
But not all of a plant may be digestible. Roughage is the portion of plant foods, such as whole grains, nuts, seeds, legumes, fruits, and vegetables, that a human’s body can't digest. However, it's an important food source for the beneficial bacteria in your digestive system. In agriculture, roughage refers to plant materials consumed by animals which adds fiber to their diet and add nutrients to strengthen their bodies.
Roughage for animals usually consists of hay, straw, grasses, corn and grains. Grinding these materials enables farmers to mix a balanced blend (“feed”) for his or her animals, and for them to consume more of it without waste. It also makes storage of the resulting feed easier to store.
After the plants and grains were harvested and threshed, the chaff (remaining portion of the plant separated from the grain) was fed into the roughage grinder. The output was then sacked and stored until needed to feed the animals.