Ammonia Anabolism in Ruminants

Abstract

Ruminal concentrations of ammonia, alpha-ketoglutaric acid, glutamic acid, and glutamine were determined in two feeding periods (alfalfa pellet only and alfalfa pellet + urea) by using fistulated Corriedal sheep. By addition of urea, the ammonia concentration exhibited significant increases. Glutamic acid decreased in contrast to glutamine in concentration, but the differences between the rations were not significant. In the urea ration period, alphaketoglutaric acid decreased but the differences were not significant. Urea increased plasma glutamine and amino-nitrogen increased significantly, whereas plasma ammonia did not.Nicotinamide adenine dinucleotide (NAD)-linked glutamic acid dehydrogenase (GAD) activity was demonstrated in the rumen mucosa and also in the mucosa of the reticulum and omasum. The NAD-linked GAD activity was also demonstrated by rumen protozoa and bacteria.Glutamine was hydrolyzed by the rumen mucosal homogenate to liberate ammonia. The cell free preparation of the rumen protozoa-rich fraction or bacteria also produced ammonia from glutamine.At high rumen ammonia concentrations, ammonia was incorporated into glutamic acid by reduction of alpha-ketoglutaric acid; furthermore, a part of the glutamic acid entered into the circulation through the rumen wall after it was converted to glutamine. These synthetic reactions should be carried out in the stomach mucosa and the rumen microorganism.