Oat hulls are a byproduct of the oat processing industry. Nutritionally, oat hulls are high in fiber, low in protein and are comparable to cereal straw as a feedstuff. As such, they are only suitable for ruminant feed. Due to the large supply, it is economically important to improve the nutritional qualities of this byproduct. Oat hulls contain hydroxycinnamic acids, which are covalently cross-linked to polysaccharides by ester bonds and to components of lignin mainly by ether bonds. These cross-links are a barrier to biodegradation and limit cell-wall degradability by rumen microorganisms. It is believed that these hydroxycinamic acids are among the factors most inhibitory to the biodegradability of plant cell wall polysaccharides.