MONENSIN TOXICITY IN A FLOCK OF OSTRICHES

A total of 42 birds from a flock of 104 farmed ostriches showed signs of toxicity after the accidental inclusion of monensin in their concen trate ration, The initial clinical signs were muscle weakness and atax ia which progressed to recumbency, dyspnoea and death, despite intensi ve supportive therapy, The serum activity of the enzymes creatine kina se, aspartate aminotransferase and lactate dehydrogenase was high in t he affected birds, indicating significant muscle pathology, Few gross lesions were identifiable postmortem, but widespread lesions of degene rative myopathy were present at the histopathological level. However, these degenerative changes were restricted to the skeletal muscle and there was no evidence of cardiomyopathy in any of the birds examined. The birds were fed a ration which contained 215 to 224 ppm monensin fo r 13 days, New clinical cases ceased to occur shortly after the withdr awal of the source of monensin, but all the individuals which showed c linical signs of toxicity died or were euthanased on humane grounds.