Distribution of anaerobic fungi in the digestive tract of cattle and their survival in faeces.

A most probable numbers procedure was used to enumerate populations of anaerobic fungi in the digesta and faeces of cattle. Anaerobic fungi were isolated from the rumen, omasum, abomasum, small intestine, caecum, large intestine and faeces. By determining the amount of digesta in each organ of the digestive tract, it was possible to estimate the total population of anaerobic fungi in cattle and make comparisons between populations in different organs. In addition to enumerating anaerobic fungi in freshly collected samples, they were quantified in digesta and faeces which had been dried at ambient temperature and stored in air for up to 9 months. These experiments showed that a higher proportion of the anaerobic fungi present in the hindgut and faeces were able to withstand desiccation than those present within the gastric and pre-gastric organs. Our results support the hypothesis that the life cycle of anaerobic fungi consists of three stages; the motile zoospore, the vegetative thallus and an aero-tolerant survival stage (cyst or resistant zoosporangium).