A
sudden death syndrome was induced in chicks and poults fed diets containing Fusarium fujikuroi, formulated to contain 0-330 mg/kg
moniliformin (M) with or without the maximum recommended therapeutic concentration of
monensin. Lesions of
monensin toxicosis were not observed. Clinical signs were referable to cardiac dysfunction (
sudden death,
dyspnea,
cyanosis, depression). Poults and chicks dying early in the study had no gross lesions or had lesions of right ventricular dilation. Treated poults and chicks dying late in the study or euthanatized at termination of the study had lesions of bilateral myocardial
hypertrophy, usually concentric. Absolute heart weights and relative heart weights, expressed as a percentage of
body weight, were significantly greater in treated birds than controls (P < 0.05), whereas
body weights were significantly less (P < 0.05). Microscopically, lesions progressed from acute myocardial degeneration to
necrosis,
fibrosis, and
hypertrophy. Ultrastructural findings were consistent with the gross and microscopic lesions. Serum
pyruvate concentrations were a useful
indicator of M-induced cardiotoxicosis. Concentrations of serum
pyruvate increased with increased concentration of dietary M, but were not affected by addition of
monensin to the diet. In chicks ingesting 40-300 mg/kg M, serum
pyruvate concentrations were significantly greater (P > 0.05) than those in controls (controls, 0.28 +/- 0.08 mmol/liter; exposed 0.38 +/- 0.11-0.55 +/- 0.13 mmol/liter). Poults ingesting 80-330 mg/kg M had significantly greater serum
pyruvate concentrations than controls (controls 0.33 +/- 0.09 mmol/liter; exposed 0.43 +/- 0.13-1.00 +/- 0.006 mmol/liter). The Vetronics System was used to evaluate electrocardiographic alterations in a limited number of chicks and poults surviving to the end of the feeding trial. Electrocardiographic alterations in poults and chicks fed diets containing > or = 40 mg/kg and > or = 160 mg/kg M, respectively, were consistent with ventricular
hypertrophy, myocardial injury, and
hypoxia. Electrocardiographic alterations were more striking in poults than in chicks. Altered myocardial metabolism due to M toxicosis, in conjunction with the unusual susceptibility of domestic poultry to altered cardiac metabolism, is believed to be the cause of the organ-specific lesions in these birds. These findings suggest that cardiac injury with subsequent alterations in cardiac electrical conductance may be a cause of the sudden deaths observed in poultry chronically intoxicated with dietary M.