The aim of the study was to evaluate and compare the protective effect of acetamide in experimental poisoning by fresh leaves of Palicourea marcgravii and monofluoroacetate (MF) in catlle, in order to prove in a practical way that this compound is the toxic principle responsible for the clinical signs and death of animals that ingested the plant. MF was administered orally in single doses of 0.5mg/kg to three cows; a few minutes later, two of these cows received, orally, single doses of acetamide (0.38 or 2.0g/kg). Two other cows ingested 1.0g/kg of P. marcgravii, and one of these cows received some minutes later 1.0g/kg of acetamide. Adequate doses of acetamide, administered right after the poisoning by P. marcgravii or MF, were able to prevented the onset of clinical signs and avoid the death of all animals. One week later, the experiments were repeated, but without the antidote. All animals not treated with acetamide showed symptoms of poisoning and died suddenly. MF and P. marcgravii caused the same clinical and pathological picture of "sudden death" in cattle. Clinically, the cattle presented palpitation, abdominal breathing, muscle tremors, engorged jugular vein with positive pulse, pollakiuria, slight loss of balance with sometimes swaying gait, the animals laying down and with the head on their flank. In the "dramatic phase", all the animals fell into lateral decubitus, stretched the limbs, made paddling movements, presented opistotonus, arrhythmia, nystagmus, and died. The "dramatic phase" lasted from 2 to 26 minutes. At postmortem examination, the heart auricles, jugulars and pulmonary veins were slightly to moderately ingurgitated; slight to marked edema of the subserosa was seen in fixation sites of gall bladder to the liver. In one cow, pulmonary edema was observed. Histopathology revealed in all cows slight to marked hydropic-vacuolar degeneration of the epithelial cells of the distal convoluted uriniferous tubules associated with nuclear pyknosis. Coagulation necrosis of individual or groups of hepatocytes and slight to moderate hepatic congestion with numerous shock corpuscles were also observed. The experimental results showed in practice that MF is the toxic principle responsible for the clinical-pathological picture and death of the cattle that ingested P. marcgravii, since acetamide acts as an efficient antidote (antagonistic effect), identical in both poisonings.
Monofluoroacetate; acetamide; Palicourea marcgravii; cattle