Roughage

Roughage is that part of food the body can't digest.

Roughage is the part of food the body can't digest.

The results of this experiment, as given in Table VII, show that sweet-clover hay is practically equal to red-clover and alfalfa and greatly superior to prairie hay for roughage for steers.

I keep telling her not to eat all that roughage for brekky; prunes, bran, and baked beans.