Rumen Undegradable Protein

Total crude protein in a ration consists of soluble protein, degradable protein and resistant crude protein. Rumen undegradable protein cannot be broken down by rumen microbes and thus becomes available for absorption in the gut. The amount of rumen undegradable protein can be determined by hanging feed material in a nylon bag in the rumen. The fraction remaining after incubation is the amount of rumen undegradable protein. The digestible fraction of rumen undegradable protein is called (intestinal) Digestible Bypass (feed) protein.

Grass contains a small amount of rumen undegradable protein, but during drying, resistance increases. Some protein-rich raw materials, such as soybean or rapeseed meal, are made more 'resistant' with formaldehyde. The percentage of rumen undegradable protein thereby increases from about 35% to more than 80%.