Investigation of chromium, cerium and cobalt as markers in digesta. Rate of passage studies

Abstract A new liquid marker, cobalt‐ethylenediamine tetraacetic acid (EDTA), and two solid markers, chromium (Cr) and cerium (Ce) mordanted plant cell walls, were investigated. Synthesis and methods of analysis are described for the markers. The Cr‐ and Ce‐cell wall complexes were tested for stability to EDTA, hydrochloric acid and rumen microorganisms. Plant cell walls were rendered indigestible by mordanting with Cr and 98% of the marker remained on the fibre after a simulated sequence ( in vitro ) of digestion. Ce‐mordanted cell walls were 35% digestible in vitro using a rumen culture, and 56% of the marker could be washed off the remaining fibre. Treatment with EDTA removed all Ce and 15% of the Cr. Hydrochloric acid (0.01 M ) had a negligible effect on the removal of Cr from the cell walls, whereas 0.1 M acid removed, on average, 10% of the marker. Losses of Cr from the mordant may be related to the quality of the preparation. Co‐EDTA was found to be comparable to Cr‐EDTA. The urinary excretion of Cr and Co was 2–3% in most animals except in rabbits, which excreted as much as 30% of the liquid markers in the urine.