The role of anaerobic gut fungi in ruminants

Abstract

Anaerobic chytridiomycete fungi are found in the gastrointestinal tracts of sheep, cattle and goats, as well as in many other domesticated ruminant and nonruminant herbivores and a wide variety of wild herbivorous mammals. They are principally found associated with the fibrous plant particles of digesta and as free swimming zoospores in the fluid phase. The presence of large fungal populations in animals consuming mature pasture or diets largely composed of hay or straw together with the production of highly active fibre degrading enzymes lead to' the belief that anaerobic fungi may have a significant role to play in the assimilation of fibrous feeds by ruminants. While many early studies focused on anaerobic fungi because of their unusual biology and metabolism, the large part of subsequent research has emphasized the biotechnological potential of their cellulases, xylanases and phenolic esterases. In recent years, the extent of the contribution of anaerobic fungi to the nutrition of ruminants has also been established through studies of fungal populations in the rumen and the dietary factors which influence them, as presented in this review. Further, we discuss the evidence supporting an important contribution of anaerobic fungal populations in the rumen to feed intake and digestion of poor quality feed by domesticated ruminants. In conclusion, the review explores some different methods for manipulating fungi in the rumen for increased feed intake and digestion.

Effect of anaerobic fungi on in vitro feed digestion by mixed rumen microflora of buffalo

“…The findings of this experiment indicate that a fungal inoculum in the rumen liquor of buffalo accelerates the rate of fermentation, digestibility of lignocellulosic feeds and the synthesis of enzymes involved in fibre degradation and confirm the previous reports on the role of rumen anaerobic fungi in fibre degradation [2][3][4]. The fungal strain FNG5 identified as Piromyces sp.…”

“…Manipulation of rumen fermentation by increasing the number or activity of lignocellulolytic micro-organisms in the rumen is one such step in this direction [1]. Among the rumen microbes, anaerobic fungi are considered to be important due to the production of highly active enzymes for lignocellulose degradation [2,3] and have a unique ability to break and penetrate the fibrous feed particles through fungal mycelium, breaking the feed particles and providing more surface area for the action of other microbes [4]. Thus rumen fungi play an important catalytic role in the digestion of poor quality fibrous feeds.…”

Interactions between microbial consortia in biofilms: a paradigm shift in rumen microbial ecology and enteric methane mitigation

“…Anaerobic fungi, in contrast, grow within the plant structures (Gordon and Phillips 1998). They produce sporangia that release zoospores that actively invade plant materials, particularly in the areas where damage to the waxy surface has occurred.…”

Rumen Microbiology: An Overview

“…Since these fungi are obligatory anaerobic, these obtain energy by fermentation of carbohydrates (Gordon and Phillips 1998 ;Trinci et al 1994 ), a process in which the energy source acts as both the electron acceptor and the electron donor. These lack mitochondria (Yarlett et al 1986 ), cytochromes, and other biochemical features of the oxidative phosphorylation pathway.…”