Estudo experimental sobre a toxidez de algumas plantas ornamentais em bovinos

Due to inquiries about the toxicity of ornamental plants to farm animals, and the few data available in the literature on this subject, feeding experiments were performed in cattle with the following plants: Allamanda cathartica, Nerium oleander and Thevetia peruviana of the Apocinaceae family, Codiaeum sp., Euphorbia cotinifolia, Euphorbia pulcherrima and Euphorbia tirucalli of the Euphorbiaceae family, Datura arborea of the Solanaceae family, Colocasia antiquorum, Dieffenbachia picta, Monstera deliciosa, Philodendron hastatum, Philodendron selloum (= P. sellowii) and Scindapsus aureus (= Epipremnum aureum) of the Araceae family, Rhododendron ledifolium and Rhododendron indicum of the Ericaceae family, and Malvaviscus arboreus of the Malvaceae family. The only plants which caused lethal poisoning were Allamanda cathartica, Nerium oleander, Thevetia peruviana and Rhododendron indicum. The letal dose for A. cathartica was 30 g/kg (causing death of 2 of 3 bovines which received this dose), for N. oleander it varied from 0,25 to 0,5 g/kg (0,25 killed 1 of 4 and 0,5 the 2 bovines which received this dose); T. peruviana caused death of 3 bovines with doses of 14,4 g/kg or more (out of 7 bovines which received these doses), and R. indicum caused death of the animal which received the highest dose which could be given, this is 29,39 g/kg, whilst a second bovine which received 29 g/kg suffered only severe poisoning. Other plants that caused severe poisoning without lethal outcome were Euphorbia pulcherrima, in doses of 16,4 and 30 g/kg, Rhododendron ledifolium in one bovine which ingested 20 g/kg, the highest dose of this plant administered. Moderate poisoning was caused by Datura arborea in one bovine which ingested 40 g/kg, by Colocasia antiquorum in 2 bovines which ingested 4 and 5,9 g/kg and by Dieffenbachia picta in 2 bovines, which ingested 3,7 and 4,8 g/kg of the respective plants. The other plants did not cause poisoning or only slight symptoms. Allamanda cathartica caused mainly manifestations of colic and the most important post-mortem and histopathological findings were severe oedema of all parts of the wall of the rumen and reticulum, and congestion of the mucosa of the remaining digestive tract. Nerium oleander caused severe cardiac arrhythmia and severe diarrhoea, sometimes with blood. The post-mortem findings were generalized hemorrhages and the main histological lesion was necrosis of heart fibres. Thevetia peruviana also caused heart arrhythmia and diarrhoea. Post-mortem and histopathological findings were negative with exception of one of the bovines which had diarrhoea, in which the contents of the rumen were putrid and those of the intestine were liquid. Euphorbia pulcherrima caused severe weakness. Datura arborea caused the symptoms of atropine poisoning. Rhododendron spp. caused mainly regurgitation without or with vomits, sialorrhoea, manifestations of colic, diarrhoea and instability. Post-mortem and histopathological findings in the only bovine that died, were negative. The plants of the Araceae family caused sialorrhoea and sublingual and submandibular oedema. It is concluded, that the rarity of the poisoning in cattle under natural conditions by these plants is due to its low palatability and the fact that normally these plants are not available to bovines, and yet that most of these plants have to be ingested in large amounts to cause poisoning. An exception is Nerium oleander, whose lethal dose is low. It is practically the only ornamental plant of those tested in this study, which according to the data in the literature has caused cases of poisoning in cattle.