COFFEE SENNA (SENNA-OCCIDENTALIS) POISONING IN CATTLE

Four 4-5-y-old cows out of a group of 20 developed a toxic myopathy ap proximately 10 d after being started on a ration contaminated with 21. 5% Senna occidentalis beans. Clinical signs included progressive muscl e weakness, incoordination of hindlimbs, reluctance to move, dragging of the tip of the hooves of the hindlimbs, and sternal and lateral rec umbency. Gross lesions included white to whitish-yellow discolored are as of several groups of skeletal muscle in various regions of the body , but more markedly In the hindlimbs. Significant histopathological ch anges were restricted to skeletal muscles with variable degrees of seg mental degenerative myopathy associated with reparative events. The ea rliest change seen at electron microscopy of affected skeletal muscles was mitochondrial swelling. More advanced changes ranged from disrupt ion of sarcoplasm and myofibrils to complete lysis of a myofiber segme nt and early regeneration. Myocardial fibers had swollen mitochondria, disruption of cristae and dense matrical globules. The epidemiology, clinical data and gross, histopathological, and ultrastructural featur es of S occidentalis poisoning in cattle are presented.