when consumed with roughage, some starches and sugars escape digestion in the equine stomach and small intestine and pass into the cecum and colon./////// microbial digestion of these and the cellulose in the roughage produces volatile fatty acids that can be absorbed and used for energy.///// microbes in the cecum and colon can also use 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 digest proteins and absorb the resulting amino acids are not readily available in the cecum or colon./////// some ureais made available to microbes by diffusing into the cecum and colon from the blood.//////fermentation and microbial digestion produce volatile fatty acids, which could lower the pH of the cecal and colonic contents to potentially harmful levels.////// the colonic epithelium secretes bicarbonate ions to buffer the pH of the contents.///////additional bicarbonate is secreted by the epithelium of the ileum, and this lowers the pH of the cecal contents.