Inert Ruthenium-phenanthrollne as a Particulate Digesta Marker in Horses

Previous studies have shown '03Ru-labelled tris (1,lO phenanthroline) ruthenium (II) chloride to be a satisfactory solid-phase marker for studying particulate digesta movement in the ruminant digestive tract (Tan et al. 1971; Faichney 1972). Subsequently, MacRab and Evans (1974) sugga the use of the inert ruthenium phenanthroline @u-P) complex to study particular digesta flow in sheep to overcome the . problems of working with a fairly strong radioactive marker (0.42 0.60 MeV gamma emission). For accurate determination of the concentration of Ru by X-ray fluorescence spectrometry, the marker must be present in the sample in excess of 50 mg/kg sample. Thus, a Ru-dose needs to be large if digesta flow rates are to be estimated over several days following a single or pulse dose. In the studies presented here the use of nonradioactive Ru-P as a marker for particulate digesta flow in horses was examined.