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Influence of Ruminal Ammonia on the Salivary Flow of Cattle

U. S. Department of Agriculture¹

Abstract

Four trials, using steers with esophageal and ruminal cannulas, were conducted to study the relationship between ruminal ammonia concentrations and the salivary flow of cattle as influenced by type of diet, urea and ruminal infusions of acidic and alkaline solutions. Results indicate that twice daily feeding of a urea containing purified diet resulted in a saliva flow that was 30% lower at 2 hr. after feeding compared to 6 hr. after feeding. The salivary flow of steers fed an isolated soy protein containing purified diet was similar at 2 and 6 hr. after feeding. Placing an equivalent amount of urea into the rumen depressed salivary flow more when steers were fed a natural diet than a purified diet. Placing a sufficient amount of urea into the rumen to produce high ruminal ammonia concentrations (80 to 110 mg. NH₃-N/100 ml. fluid) and symptoms of ammonia toxicity, reduced salivary flow to only 20% of normal. Intraruminal infusions of alkaline or acid solutions had little effect on salivary flow. Infusions of urea solutions, resulting in high ruminal ammonia concentrations, resulted in depressed salivary flow, but the depression was much more pronounced at a high ruminal pH (>7.5) than at a low ruminal pH (<6.0).

¹ A.R.S., Animal Husbandry Research Division, Beltsville, Maryland.