Ammonia Toxicity in Cattle. III. Absorption of Ammonia Gas from the Rumen and Passage of Urea and Ammonia from the Rumen to the Duodenum

Abstract

Ammonia gas infused into the dorsal vault of the rumen of cattle at 200 ml per min increased the ammonia concentration in rumen fluid expressed from the hay mat but failed to increase the concentration in the rumen fluid in the ventral sac of the rumen below the hay mat or in the jugular blood. The animals did not exhibit ammonia toxicity. Rumen motility was markedly reduced which may have impaired the mixing of the contents. When urea was placed in the rumen (.5 g per kilogram body weight), rumen fluid pH, and rumen fluid and blood ammonia concentrations were elevated, rumen stasis occurred, and ammonia toxicity resulted. No ammonia was present in the gas collected from an esophageal fistula. Thus, because rumen atony prevented eructation, apparently gaseous ammonia in the dorsal vault of the rumen did not bypass the liver by being eructated and forced to the lungs for absorption. Placing .6 g urea per kilogram body weight in the rumen of a cow adapted to urea for 12 weeks produced ammonia toxicity and substantially elevated concentrations of rumen fluid ammonia and urea; whereas, duodenal fluid ammonia and urea concentrations increased slightly. This suggests that substantial quantities of ammonia were removed between the rumen and duodenum. Copyright © 1977. American Society of Animal Science . Copyright 1977 by American Society of Animal Science.