Degradation of maize protein in rumen contents Influence of ammonia concentration

Abstract

1. The influence of ammonia concentration on the distribution of nitrogen derived from opaque-2 maize uniformly-labelled with15N has been investigated during short-term in vitro incubation of bovine rumen contents.2. Less15N derived from maize was found in the non-protein-N (NPN) fraction during incubation without added NH3than with added NH3, due entirely to differences in the amount of N derived from maize in the NH3fraction.3. From calculations based on the transfer of N derived from maize to the NPN pool and to a bacterial fraction, it was concluded that degradation of maize protein was not influenced by NH3concentration within the examined limits.4. The decrease in relative amount of N derived from maize in the NH3fraction at low concentrations of NH3, together with evidence for an increased fractional turnover rate of NH3-N suggests that a deficient supply of NH3is compensated for by increased catabolism of nitrogenous compounds derived from the rumen micro-organisms.