Plantas tóxicas para ruminantes e equídeos no Brasil.

Abstract

The papers that comprises this thesis derive from studies of plant poisoning, conducted by a research group on toxic plants from the National Institute of Science and Technology for Control of Poisonous for Plants, based in Veterinary Hospital, Federal University of Campina Grande in Patos, Paraíba. The first paper is a review of the economic importance, epidemiology and control of plant poisonings in Brazil. The expected annual losses by animal deaths caused by toxic plants was estimated in 820,761 to 1,755,763 cattle, 399,800 to 445,309 sheep, 52,675 to 63,292 goats, and 38,559 horses. Most of the losses are caused by Palicourea marcgravii, Amorimia rigida, Senecio spp., Pteridium aquilinum, Cestrum leavigatum, and Ateleia glazioviana in cattle, Brachiaria spp in cattle and sheep, and Ipomoea asarifolia and Nierembergia veitchii in sheep, plants containing swainsonine (Ipomoea carnea, Turbina cordata and Sida carpinifolia) in goats and Brachiaria humidicola and Crotalaria retusa in horses. The main epidemiological factors that determine plant poisonings include palatability, hunger, thirst, social facilitation, unaware of the plant, access to toxic plants, toxic dose, ingestion period, variations in toxicity and resistance to poisoning of animals. The methods of control and prevention recently developed in Brazil include: biological control, conditioned food aversion, using non-toxic varieties of forages, use of animals resistant to poisoning, and techniques of inducing resistance. The second paper was the result of a research project that aimed to prove the hypothesis that, in horses, the dehydropirrolizidine alkaloid monocrotaline present in the seeds of Crotalaria retusa only produces liver injury, while dehydropirrolizidine alkaloids present in the seeds of Crotalaria juncea (isohemijunceines, trichodesmine and junceine) produce lung injury. The results confirmed the hypothesis that while monocrotaline cause liver injury (centrilobular necrosis) alkaloids contained in C. juncea cause pulmonary lesions (proliferation of Clara cells and fibrosis). The third paper reports the clinical signs, pathology and control measures of Marsdenia spp. poisoning in ruminants the semiarid region of northeastern Brazil. The poisoning was characterized by nervous signs, with non significant histological lesions. Nervous signs similar to those observed in the spontaneous poisoning were induced experimentally by administration of roots of M. hilariana for goats and leaves and roots of M. megalantha for sheep.