What are soybean hulls or soyhulls: Soybean hulls are a by-product of soybean processing for oil and meal production. Typically, soybean hulls do not require special processing to feed. However, soybean hulls have urease (an enzyme), activity which can be a problem in rations containing urea. Heat treatment destroys the urease activity. Soybean hulls which have been heat treated are referred to as soybean mill run, soybean flakes, or soybran flakes.