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The influence of anaerobic fungi on rumen volatile fatty acid concentrations in vivo

Published online by Cambridge University Press:  27 March 2009

R. Elliott
Affiliation:
Department of Agriculture, University of Queensland, St Lucia, Queensland, Australia 4067
A. J. Ash
Affiliation:
Department of Agriculture, University of Queensland, St Lucia, Queensland, Australia 4067
F. Calderon-Cortes
Affiliation:
Department of Agriculture, University of Queensland, St Lucia, Queensland, Australia 4067
B. W. Norton
Affiliation:
Department of Agriculture, University of Queensland, St Lucia, Queensland, Australia 4067
T. Bauchop
Affiliation:
Department of Biochemistry, Nutrition and Microbiology, University of New England, Armidale, N. S. W. Australia 2350

Summary

Elimination of the rumen anaerobic fungi from sheep fed chemically-treated barley straw diets resulted in elevated proportions of propionic acid in rumen liquor (from ca. 0·15 to 0·30). Subsequent inoculation of these sheep with a pure culture of fungus decreased propionate concentrations within 3 days to the levels observed in control animals that possessed abundant fungal populations throughout the experiment.

Confirmation that propionate itself was not responsible for the elimination of the fungi was provided by the results of a second experiment in which intraruminal infusions of propionic acid failed to reduce fungal growth or prevent recolonization in sheep previously rendered fungi-free.

In a third experiment with sheep fed untreated barley straw, monensin supplementation produced the well known elevation of propionate concentrations. However, this treatment also resulted in the elimination of rumen anaerobic fungi from the animals. The magnitude of the increased concentration of rumen propionic acid, resulting from the elimination of the anaerobic fungal flora, indicates an important role for the fungi in the fermentation of high-fibre diets. In addition, these findings indicate that the well known elevation of propionate levels produced by monensin may likewise be effected directly by removal of the rumen anaerobic fungi.

Type
Research Article
Copyright
Copyright © Cambridge University Press 1987

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