CLINICAL MEDICINE

Summary In order to test the hypothesis that ruminal drinking in calves can lead to d-lactic metabolic acidosis, ruminal acidosis was induced in nine calves by intraruminal application of untreated whole milk via a stomach tube. The amount of the daily force- fed liquid was 3 · 1 l. The experimental design called for an end of intraruminal applications if two or more of the following signs were observed: severe depression, estimated degree of dehydration >10%, absence of sucking reflex, lack of appetite for two consecutive feedings, severe metabolic acidosis with calculated Actual Base Excess (ABE) <)15 mmol/l. The pro- cedure was scheduled to be discontinued on the 17th day of experiment. The onset of ruminal acidification occurred rapidly, and mean pH value fell from 6.70 (±0.48) to 4.90 (±0.38) after the first application. The following days the pH values varied between 4 and 5. Rumen acidity was characterized biochemi- cally by a significant increase in bothisomers of lactic acid. The effects of the intraruminal administration on the calves were detrimental; eight of nine calves showed an acute disease pro- cess. According to the pre-established clinical standard, seven of nine calves were removed from the intraruminal feeding sche- dule. All but one of the calves developed severe systemic acidosis. The increase in anion gap demonstrated the net acid load. In all the calves d-lactate levels were found to show a significant and rapid increase. On the contrary, l-lactate never deviated from physiological levels. These observations confirm that, in young calves as in adult cattle, ruminal acidosis may lead to a clinically manifested d-lactic metabolic acidosis.