Characteristics and effects of ruminal proteolysis on ruminant nutrition

Abstract

To determine if amino acids are released equally during ruminal protein degradation, 4 hr ruminal in vitro degradation was determined on 10 proteins. Correcting for recovery of each amino acid, net release of 12 amino acids during protein degradation was calculated. Total release (molar percent of 12 amino acids studied) ranged from 8.6% for 60 min autoclaved CSM to 50.3% for casein. With all proteins, there were significant differences (P < .05) in mean releases of amino acids. Linear regressions, using the 10 proteins, indicated that there was a correlation in the extent release of each amino acid during protein degradation. The coefficient of determination (r('2)) for each amino acid was: lysine, .91; histidine, .93; arginine, .96; threonine, .86; glycine, .50; alanine, .95; valine, .97; methionine, .93; isoleucine, .96; leucine, .89; tyrosine, .92; phenylalanine, .94. The amino acids predicted to be degraded to a higher extent than total degradation were lysine, arginine, histidine, alanine and phenylalanine. Predicted degradations of threonine, glycine, valine, isoleucine, leucine, tyrosine and methionine were lower than total degradation. ...