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Nutritional availability of amino acids from the rumen anaerobic fungus Neocallimastix sp. LM1 in sheep

Published online by Cambridge University Press:  27 March 2009

S. K. Gulati
Affiliation:
Commonwealth Scientific and Industrial Research Organisation, Division of Animal Production, PO Box 239, Blacktown, NSW 2148, Australia
J. R. Ashes
Affiliation:
Commonwealth Scientific and Industrial Research Organisation, Division of Animal Production, PO Box 239, Blacktown, NSW 2148, Australia
G. L. R. Gordon
Affiliation:
Commonwealth Scientific and Industrial Research Organisation, Division of Animal Production, PO Box 239, Blacktown, NSW 2148, Australia
P. J. Connell
Affiliation:
Commonwealth Scientific and Industrial Research Organisation, Division of Animal Production, PO Box 239, Blacktown, NSW 2148, Australia
P. L. Rogers
Affiliation:
Department of Biotechnology, University of New South Wales, PO Box 1, Kensington, NSW 2033, Australia

Summary

The rumen anaerobic fungus Neocallimastix sp. LM1 was specifically labelled in batch culture with either [14C]lysine, [14C]lysine + [3H] tyrosine, [14C] methionine, or [35S] sulphide. Fractionation of acid hydrolysates of fungal biomass on an amino acid analyser showed that the labelled amino acids were directly incorporated into fungal protein with little or no degradation. [35S] Sulphide was incorporated into cysteine and methionine.

Absorption of amino acids from the small intestine was measured in sheep with permanent fistulae in the abomasum and terminal ileum, by introducing radiolabelled fungal biomass into the abomasum together with Cr-EDTA as the marker for digesta flow. The proportions of [14C] lysine (Expt 1), [14C] lysine + [3H] tyrosine (Expt 2), [14C] methionine (Expt 3) and the sulphur amino acids from [35S] sulphide (Expt 4) which appeared unabsorbed at the terminal ileum averaged 0·13, 0·07 + 0·08, 0·13 and 0·02, respectively. These proportions reflect the high digestibility of certain essential amino acids and the sulphur amino acids of fungal proteins. The results indicate that the true fractional digestibility of fungal proteins is c. 0·9. Consequently, a large biomass of anaerobic fungi in rumen digesta would be expected to provide a valuable source of digestible amino acids to ruminants.

Type
Research Article
Copyright
Copyright © Cambridge University Press 1989

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