EFFECT OF LACTIC ACID ADMINISTRATION ON RUMEN MYOELECTRICAL ACTIVITY AND PRESSURE CHANGES IN THE SHEEP

Pressure changes and myoelectrical activity in the ovine rumen were investigated following the surgical implantation of fluid-filled, balloon-tipped tygon tubes and paired fine needle platinum electrodes. The correlations among rumen pressure change and myoelectrical spike burst duration, frequency and magnitude data from 4477 one-minute periods were determined. Myoelectrical spike burst duration was used as the criterion for examination of lactic acid-induced myoelectrical activity. Rumen myoelectrical activity was not affected by intraruminal or intravenous introduction of lactic acid. However, after lactic acid was infused intraduodenally, a short period of total inhibition of activity occurred, which was followed by a rapid recovery to near normal levels despite the continuation of the infusion. Short periods of inhibition and recovery continued for up to 1 h following termination of infusion. The results suggest that inhibition of rumen myoelectrical activity in lactic acidosis may be caused primarily by lactic acid produced in the rumen entering the intestine and causing a stimulation of the enterogastric reflexes.