STUDIES ON INTESTINAL DIGESTION IN SHEEP .I. USE OF CHROMIC OXIDE AS AN INDIGESTIBLE MARKER

1. The use of chromic oxide (Cr2O3) as an indigestible marker for studies on intestinal digestion in sheep has been examined. The sheep used were equipped with a cannula into the rumen and a re-entrant cannula in the proximal duodenum; some also had a re-entrant cannula in the terminal ileum. The marker was administered twice daily in the form of Cr2O3-impregnated paper, through the rumen cannula. 2. Recovery of Cr2O3 in the faeces, based on 7-day collection periods, was satisfactory, the mean recovery for all seven experiments being 99.6 0.7%. In seventeen 24 h collections of digesta entering the proximal duodenum, the mean recovery of the daily dose of marker was 83.7% (range 63.6-148.4%); in eleven such collections at the terminal ileum the mean recovery was 77.3% (54.0-90.0%). 3. Detailed examination of the concentrations of Cr2O3 in dry matter was made with individual samples taken during single 24 h periods for five duodenal and three ileal collection periods. There were always marked variations in these concentrations. It is concluded that use of short collection periods to give mean values for the flow of digesta throughout the 24 h, at particular points along the tract, may lead to large errors. © 1969, The Nutrition Society. All rights reserved.