Detection of microbial protein synthesis in the small intestine of sheep using an intraduodenal 15N-urea infusion]

Sheep (3 animals, 50 kg LW) with reentrant cannulas in duodenum and at the end of the ileum received 700 g hay and 800 g alfalfa pellets per animal and day. In a previous 1st period of three days duodenal digesta and in a 2nd period of four days ileal digesta were collected and stored deep frozen. In the main period the digesta flow was interrupted for 28 hours. The duodenal and ileal digesta were collected quantitatively. The previously collected duodenal and ileal digesta portions were introduced hourly. The duodenal digesta was supplemented with 15N-labelled urea for a 24 hour period. 4.5% of the introduced 15N-excess were detected at the end of the ileum in the 24 hour period. 5.6% of the 15N-excess at the end of the ileum were incorporated in bacterial protein. It was measured that the ileal digesta contained 4.62 g N in the TCE precipitable fraction and 24.4% of the TCE precipitable N-fraction was bacterial nitrogen.