[Endogenous urea in the intestinal tract and its significance in nitrogen metabolism in ruminants].

In the first series of experiments we studied in wethers the percent involvement of various parts of the intestinal tract (from duodenum to cecum) in the secretion of endogenous urea. We found out the following involvement of the given intestinal parts secreting urea to duodenum during 24 hours: bile 6.33%, pancreatic juice 1.85%, through the wall of the front part of jejunum 55.71%, through the wall of the rear part of jejunum 32.25% and through the cecum wall 3.86% of nitrogen of endogenous urea. The urea secreted to the mentioned parts represents one third of the total amount of endogenous urea transported to the entire gastrointestinal tract. Possibilities of utilizing this endogenous source of nitrogen in the organism of ruminant animals were studied in further experiments where 15N-labelled urea was applied to the cecum. We found out that more than four fifths of endogenous urea secreted to the small intestines returned to the metabolic circulation and that only less than one fifth was excreted, not being utilized anew in the organism.