An assessment of the use of chromic oxide as a marker in protein digestibility studies with Haliotis midae L

A comparison between the total faecal collection method and chromic oxide marker technique in determining apparent protein digestibility coefficients in Haliotis midae, revealed that while the former was not a suitable methodology for use in this species, the latter produced replicable and reliable results. While three distinct types of faecal material were described, correlation analysis revealed a significant correlation between faecal chromic oxide and faecal protein ( r 2=0.89). It was established that at a dietary inclusion rate of 0.5%, the chromic oxide was inert, was not absorbed by the animal, did not interfere with the digestive process, and moved through the intestine at the similar rate to the protein. Of the three types of faecal material described, Type 1 faeces provided the most reliable estimates of apparent protein digestibility in this species.