Outbreak of monensin poisoning in cattle due to supplementation error

ABSTRACT: Iatrogenic intoxications occur in domestic animals. Mortality was observed in a group of calves, reaching 20 deaths until the day of the technical visit, with or without sudden clinical signs, on a farm in the city of Pires do Rio, State of Goiás, Brazil. Deaths after the visit were not accounted systematically. Clinical signs included muscle weakness, ataxia, recumbency, bilateral jugular distention, and death. Suspected diagnosis of poisoning by ionophore antibiotics was made based on clinical and laboratory findings from nine animals, which included high plasma CK and LDH levels, as well as on anatomopathological findings of a recently dead calf, which showed myocardial and skeletal muscle degeneration and necrosis. Monensin overdose (25.5 µg/kg in skeletal muscle and 209.4 µg/kg in the liver) was detected by liquid-chromatography and mass-spectrophotometry analysis, contributing to the confirmation of ionophore poisoning diagnosis.