The effect of sterols and haemin on the growth of the rumen ciliate Ophryoscolex caudatus and some other Entodiniomorphid protozoa

Seven isolates of Ophryoscolex caudatus have been cultured anaerobically in vitro (at a population density of 56/ml) for an average of 18 months each in the presence of bacteria on a reduced buffered salts medium containing prepared fresh rumen fluid with the daily addition of ground wheat and dried grass and with twice weekly dilution of the culture with an equal volume of fresh medium. The ground wheat and dried grass could be replaced by ground wheat coated with β-sitosterol, stigmasterol, ergosterol or α-spinasterol and with β-sitosterol the population density increased to 110/ml. Haemin further increased the population density obtained in the presence of sterol by 9–160%. The population density of cultures of Epidinium ecaudatum caudatum was also increased by sterols and haemin, that of Polyplastron multivesiculatum by sterols only, and some sterols and haemin, under certain conditions, increased that of Entodinium caudatum.