<!--Rumen protein fermentation 

Microbes in the rumen ferment most of feed pro­teins and non-protein nitrogen (NPN) just as extensively as they modify feed carbohydrates (Castrillo and Balcells, 2002). Nitrogenous feed materials that are digested microbes are considered to be ruminally degradable crude protein (RDP), which is the source of N from which microbial protein is synthesized by microorganisms. Microbial protein is then the main source of digestible protein for the animal (Castrillo and Balcells, 2002).  A variable fraction of the dietary true protein, how­ever, either remains undegraded or is only partially degraded. This frac­tion passes to the lower gut and augments the microbial protein available for intestinal digestion. In the context of dietary management and feeding standards, this fraction is often referred to as ‘escape protein’, ‘by-pass pro­tein’ or ‘undegraded dietary protein’ (UDP) (Castrillo and Balcells, 2002).