EN
A case of acute poisoning of nine horses accidentally fed Polfamix R-1 designated for cattle was described. Polfamix R-1, vitamin-mineral supplement contains 3.25 g of monensin per 1 kg. Each horse was fed about 200 g of the supplement (approx. 650 mg of monensin per 1 horse). After the Polfamix administration, two horses died suddenly and three other sick animals were observed for 7-10 days. Clinical signs of poisoning were characterized by motor and cardio-vascular disturbances. Residues of monensin were found in the kidney, heart and in the content of the two horses which died within 2 days after consuming monensin. The levels of the drug were 690 and 580 mcg per 1 kg in the kidneys of two horses and in the content of the stomachs - 440 and 360 mcg/kg, respectively. Only some traces of monensin were noted in the hearts. However, no presence of monensin was found in the samples of the three horses which died after a week.