Ammonia Intoxication Resulting from Urea Ingestion by Ponies

Abstract

SUMMARY The mean urease activity of cecal fluid from 4 ponies fed a hay-grain ration was 18.6 ± 3.9 Sumner units/ml., which is about 17 to 25% of values reported from bovine rumen fluid. Seven of 8 ponies given 450 Gm. of urea by mouth died. The sequence of increases in blood metabolites observed was as follows: urea, ammonia, α-ketoglutarate, glucose, and finally pyruvate. The sequence of events is consistent with the hypothesis that inhibition of α-ketoglutarate decarboxylation is the primary site of ammonia toxicosis. The biochemical changes occurred before any clinical signs were apparent. The clinical signs were those of severe central nervous system derangement and were similar to those observed in horses with severe liver malfunction.