A chronic disease with cardiovascular and respiratory involvement in lactating cows was diagnosed in a dairy herd. In the clinical examination tachycardia and diarrhea were observed. On postmortem examination in 6 cows, petechial hemorrhages at the epicard, hepatomegaly, enhancement of lobular pattern of liver, pulmonary edema and consolidation were observed. Histopathological examination revealed necrosis and degeneration of heart muscles, severe hemorrhage and infiltration of inflammatory cells (especially lymphocytes) at the myocardium. Hepatic lesions were included; periportal fatty changes, hepatocellular atrophy in centrilobular zone and substitution of them by red blood cells and connective tissue. Pulmonary tissue was very hyperemic and alveoli were filled with edema fluid and hemosiderophages. Interstitial pneumonia and thickening of alveolar septa due to infiltration of mononuclear inflammatory cells and fibrosis were the predominant lesions too. On the basis of history, the long time usage of monensin, clinical signs, pathological and toxicological finding, chronic or subacute monensin poisoning was diagnosed definitely. The problem was resolved after decrease amounts of monensin.

کلمات کلیدی