Effects of disturbances of acid-base equilibrium on the activity of the rumen.

The effect on ruminal motility of NH4- or Na-acetate and Na- or K-lactate of various pH and doses infused into the jugular vein (i.v.) or carotid artery (i.a.) was studied in sheep with ruminal fistula I.v. infusion of NH4-acetate whenever it was accompanied by a considerable increase of the blood NH4 level potently inhibited the amplitude and frequency of ruminal contractions. I. a. administration produced more rapid and more apparent responses and a slightly elevated venous ammonia concentration than did the i.v. infusion. Thus the augmented blood ammonia level not only affected the smooth muscles and peripheral nerve endings but also inhibited the vegetative centres of the central nervous system. Infusion of Na-acetate and Na- or K-lactate solutions induced compensated acidosis or alkalosis which reduced the amplitude of ruminal contractions and produced respiratory disturbances. The latter were more apparent in alkalosis. In uncompensated acidosis or alkalosis, ruminal motility was permanently inhibited or abolished. The results appear to show that in not properly fed ruminants the frequently observed and long lasting compensated acidosis or alkalosis might influence the activity of the vegetative centres thus further metabolic disturbances and impaired gastrointestinal activity might follow the shifts in acid-base equilibrium.