A study on the use of radioactive or non-radioactive ruthenium (Ru) as a particulate marker has been carried out using sheep. The aim of the study was to see wether both markers could produce similar results in studying the digestive phisiology of ruminants. Both markers were mixed together in a solution and administered into the rumen of sheep through a fistula. The digestion rate of feed in the gastro-intestinal tract was observed from the change of marker concentration in samples collected from abomasum and faeces at a given interval after the markers were dosed into the rumen. It was found that both markers gave similar results particulary on the observations using faecal samples. The possible cause of the dis-crepancy between markers on the abservations using abomasal digesta are discussed. It could be concluded that one of the marker may be used and its selection depends on the purpose and budget available. B. Bakrie*, R.M. Murray**, dan J.P. Hogan**** Balai Penelitian Ternak. ** Graduate School of Tropical Veterinary Science., Australia *** Davies Laboratory, CSIRO., Private mail Bag., Australia.
