Poisoning of cattle by mascagnia pubiflora in Mato Grasso, Brazil

Abstract

Mascagnia pubiflora (Juss.) Grisebach, of the Malpighiaceae family, was identified as an important cause of mortality in catlle from the southern Mato Grosso. Two varieties of the plant were observed, a smooth leaved and a velvet leaved form. Experiments in 30 bovines revealed that both varieties had the same toxicity for cattle, but their toxicity varied during the year. In August/September (the dry season of the year) the plant was actively growing, flowering and seeding and during this period the lethal dosage was 5g/kg body weight. In April/May (at the end of the rainy season), when the plant had mature leaves the lethal dosage was 20 g/kg. The toxicity of the dried leaves was diminished if they were kept for several months at room temperature. In one experiment with the dried leaves the plant showed no cumulative effects and did not induce tolerance. The clinical picture of the poisoning was quite uniform in all the experimental animals. Some of them (6/15) were found dead the morning after the administration of the plant; they died between 16 and 22% hours after ingestion of the plant. In those animals where the poisoning was studied clinically (9/15), symptoms were first seen 16 to 25 hours after the administration of the plant. Death occurred within a period of a few minutes to 49% hours after the onset of symptoms; but in all the experimental cases, even in those with a long evolution, there was a final dramatic stage, of "sudden death", which lasted only minutes. The clinical signs of poisoning were reluctance to stand up, staggering gait, muscle tremors, and lying down abruptly especially when driven around. These signs could be precipitated or intensified by exercising the animal. Sooner or later, depending partly on the exercise, these signs suddenly became very intense; the animal fell on its side, made violent movements with its legs and died, and this last stage lasted only minutes. The effect of exercise was enhanced after the animals were left in the sun. Post-mortem examination revealed no abnormal findings. The most interesting histopathological lesions consisted of hydropic degeneration of the epithelial cells of the distal convoluted kidney tubules, but this was not seen in all the experimental animals (6/15).