When consumed with roughage, some starches and sugars escape digestion in the equine stomach and small intestine and passes into cecum and colon. Microbial digestion of these nutrients and cellulose in the roughages produce SCFA that can be absorbed and used for energy in the metabolic processes. Microbes in the cecum and colon also uses nonprotein nitrogen sources (urea) for the production of microbial proteins. However, these have limited nutritional value to the horse, because the gastrointestinal mechanisms necessary to digestion proteins and absorb the resulting amino acids are not readily available in the cecum or colon. Some urea is made available to microbes by diffusing into the cecum and colon from the blood.