Intoxicação por Crotalaria retusa em pequenos ruminantes.

Abstract

Crotalaria retusa poisoning is frequent in Paraíba primarily affecting equines, followed by sheep and cattle. This dissertation is formed by two papers. The first paper of the dissertation reported the first outbreak of poisoning by pyrrolizidine alkaloids produced by C. retusa in goats and the experimental reproduction of the disease in this species also, emphasizing clinical and pathological characteristics. C. retusa, estimated to contain about 4.96% monocrotaline (MCT) in the seeds, was associated with a natural poisoning outbreak in goats. From a total of 30 goats, 4 sickened and died. The poisoning was experimentally reproduced by the administration of C. retusa seeds containing about 4.49% of MCT. Thus, one of three goats given a single dose of 5 g/kg bw of seeds (248 mg MCT/kg bw) and two goats given a single dose of 347 mg MCT/kg bw showed acute clinical signs and were euthanized 10-11 days after dosing. Clinical signs and gross and histologic lesions were characteristic of acute centrilobular liver necrosis. The second paper,aimed to determine the duration of the resistance of sheep to poisoning by C. retusa after the end the administration of continuous non-toxic doses of seeds. Ten sheep were divided into 3 groups of 3 animals each and one control sheep. To induce resistance sheep in groups 1, 2 and 3 received during 20 days, daily doses of 2 g/kg of C. retusa seeds, followed by 7 daily doses of 4g/kg. To determine the duration of resistance the sheep in groups 1, 2 and 3 were challenged orally, 3, 7 and 15 days, respectively, after receiving the last dose of 4 g/kg, with a single dose of 5 g/kg. Sheep of groups 1 and 2 did not develop signs of poisoning. Two sheep of the group challenged 15 days after the end of the resistance induction period showed acute poisoning and died. These results suggest that, in sheep, resistance to monocrotaline, induced by repeated non-toxic doses is of short duration, from 7 to 15 days.