THE ROLE OF ANAEROBIC GUT FUNGI IN RUMINANTS

Anaerobic chytridiomycete fungi are found in the gastrointestinal trac ts of sheep, cattle and goats, as well as in many other domesticated r uminant and nonruminant herbivores and a wide variety of wild herbivor ous mammals. They are principally found associated with the fibrous pl ant particles of digesta and as free swimming zoospores in the fluid p hase. The presence of large fungal populations in animals consuming ma ture pasture or diets largely composed of hay or straw together with t he production of highly active fibre degrading enzymes lead to the bel ief that anaerobic fungi may have a significant role to play in the as similation of fibrous feeds by ruminants. While many early studies foc used on anaerobic fungi because of their unusual biology and metabolis m, the large part of subsequent research has emphasized the biotechnol ogical potential of their cellulases, xylanases and phenolic esterases . In recent years, the extent of the contribution of anaerobic fungi t o the nutrition of ruminants has also been established through studies of fungal populations in the rumen and the dietary factors which infl uence them, as presented in this review. Further, we discuss the evide nce supporting an important contribution of anaerobic fungal populatio ns in the rumen to feed intake and digestion of poor quality feed by d omesticated ruminants. In conclusion, the review explores some differe nt methods for manipulating fungi in the rumen for increased feed inta ke and digestion.