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

• Published in: The Journal of agricultural science 1989-12, Vol.113 (3), p.383-387
• Main Authors: Gulati, S. K., Ashes, J. R., Gordon, G. L. R., Connell, P. J., Rogers, P. L.
• Format: Article
• Language: English
• Subjects: Biological and medical sciences; Fundamental and applied biological sciences. Psychology; Stomach; Vertebrates: digestive system
• ISSN: 0021-8596; 1469-5146
• DOI: 10.1017/S002185960007009X

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.