Cerebro-cortical necrosis (C.C.N.) in calf. An experimental reproduction of the disease.

In four ruminant calves a state of thiamine deficiency was brought about with a thiamine antagonist, amprolium. Twice daily the calves were given Amprolmix® containing 25 amprolium through a stomach tube. The dosage was 350–500 mg/kg body weight daily during the entire experimental period. After 31 days the first calf showed fully developed symptoms; two other calves fell ill after another four and eight days respectively. The fourth calf was killed before the disease became clinically manifest. In all calves cerebrocortical necroses were found on histological examination. The clinical picture is described. It was similar to that in spontaneous C.C.N. In the calves exhibiting fully developed symptoms a moderate rise was observed in the pyruvate kinase and a heavy rise in the creatine Phosphokinase activity. On several occasions the total quantity of thiamine (free + phosphorylated) in the blood exceeded the upper normal limit without any extra supply of thiamine being given. Only on one occasion was a lowering observed, to a value just below the lower limit of normal variation.