Enzymatic Determination of the Protein Quality of Individual Rumen Bacteria

Abstract

Protein quality of individual rumen bacteria was studied using an in vitro enzymatic digest system, and a protein quality index (NPU_enx) was computed from egg ratios. Depending upon the individual strain the NPU_enx values ranged from 37 to 80, whereas control digests with casein gave NPU_enx values of 86.5 and 73.6. The proportion of the essential amino acids being released as free amino acids during the digest varied between 2.5% and 52.6%. Furthermore, the distribution of the essential amino acids within this fraction varied markedly also. It is suggested that modification of the bacterial population may be an important factor with respect to the nitrogen status of the animal and its response to dietary changes.