Amino Acids Released during Protein Degradation by Rumen Microbes

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Abstract
An in vitro procedure was used to study the profile of individual amino acids released during ruminal protein degradation. Four-hour incubations were conducted using a rumen inoculum containing 1 mM hydrazine, an inhibitor of deamination. Recoveries of 12 free amino acids, added in the form of casein hydrolysate, ranged from 76 to 149%. Correcting for recovery of each amino acid, release of these 12 amino acids during degradation of 10 protein sources was determined. Released amino acids were assumed to represent those degraded in the rumen. Individual amino acids were not released in proportions equal to amounts present in the protein. For example, 50.7% of the 12 selected amino acids were released from casein, with a range of 27.3 (glycine) to 74.1% (arginine). Protein degradation ranged from 12.3% (autoclaved cottonseed meal) to 59.2% (casein) during 4-h incubations. Individual amino acid release was correlated to total release of the 12 amino acids. Coefficients of determination (R2) ranged from .50 for glycine to .97 for valine. Regression equations indicated that alanine, arginine, histidine, lysine and phenylalanine were degraded to an extent greater than total degradation. Predicted degradations of threonine, valine, isoleucine, leucine, methionine, glycine and tyrosine were similar to or lower than total degradation. Copyright © 1984. American Society of Animal Science . Copyright 1984 by American Society of Animal Science.