Influence of Rumen Fluid Source upon Establishment and Cultivation in vitro of the Rumen Protozoon Entodinium

SYNOPSIS. Favorable conditions for establishing Entodinium cultures in vitro were provided by rendering the inoculum almost free of other genera of rumen ciliates, inoculating at a final concentration of 30,000 entodinia per ml, providing 0.2 mg rice starch per ml, but principally by including an appropriate rumen fluid in the media. Rumen fluids collected from animals with high concentrations of entodinia in vivo, in general, were superior in supporting entodinia in vitro than were those collected from animals having low concentrations of entodinia in vivo. Rumen fluids from lambs were improved by clarification (centrifuging at 25,000 × g for 20 min), but clarification destroyed the ability of rumen fluids from pregnant ewes to support entodinia in vitro. One or more factors occurring in the supernatant portion of pooled, clarified lamb rumen fluid stimulated entodinia in vitro.