Studies on the Role of Rumen-Anaerobic Fungi and Protozoa in Fibre Digestion

Abstract

The objectives of this study were: 1. To evaluate the effects of defaunation of the rumen on the growth of rumen anaerobic fungi and on fibre digestion in sheep given high-fibre diets. 2. To determine the contribution of rumen-anaerobic fungi to plant cell wall digestion in vitro. Determination of pool size of anaerobic fungi in the rumen is important in order to study the contribution of these microorganisms to feed digestion relative to other rumen inhabitants. Two methods used in the present studies, viz. counting the numbers of sporangia on feed particles and culturing the zoospores in roll tubes containing agar medium plus antibiotic, resulted in large variations between animals and diets, suggesting that these methods cannot be used to determine the fungal biomass accurately. However, they may be used for comparing the relative numbers of anaerobic fungi present in the rumen between treatments under the same experimental conditions. ... It was concluded that on high-fibre diets the presence of rumen protozoa may be disadvantageous because they appear to reduce the pool size of cellulolytic microorganisms (bacteria and fungi) in the rumen. Although information on enzymic activities of anaerobic fungi on fibre digestion now seems clear from the literature, the major question of the magnitude of the contribution made by fungi to fibre digestion remains to be answered. For these reasons, the development of a reliable method for assessment of fungal biomass in the rumen is a major priority for future research.