The Production of Cerebrocortical Necrosis in Ruminant Calves by the Intraruminal Administration of Amprolium

SUMMARY Six weaned calves were fitted with a rumenal fistula tube. Two of the calves were subsequently given daily intraruminal doses of Amprolium* at the level of about 1 per cent by weight of the diet, two calves were given similar doses of Amprolium with added thiamine in the ratio of 500 to 1, two were left as untreated controls. Before and during the experiment blood pyruvate and lactate, plasma pyruvate kinase and urinary thiamine were assayed. Immediately after death samples of urine, liver and brain were taken for thiamine assay. Both calves given Amprolium alone developed cerebrocortical necrosis. There was no significant difference between the urinary thiamine of the three pairs of calves. The blood level of pyruvate, lactate and pyruvate kinase was increased in the Amprolium-dosed calves. These findings are briefly discussed with reference to earlier work. It is suggested that the proportion of Amprolium to thiamine was a significant factor in the development of cerebrocortical necrosis.