Toxic plants affecting livestock in South America: Review of epidemiology, diagnosis, control, economic impact and implications to human health1

Abstract

The objective of this paper is to review the information on toxic plants for ruminants and horses in South America, a continent in which there are 237 plants known to be toxic for livestock. Predisposing factors for plant toxicity include parts or vegetative state of the plants consumed, sprouting after rains, toxic dose, social facilitation, palatability, hunger, thirst, naivete, ingestion period, susceptibility/resistance, transportation, climatic alterations, and environmental degradation. Toxic plants can be forage or non-forage species. The latter can be invasive plants from other regions or from the same region. For the diagnosis of plant poisoning caused by known active compounds, the detection of these substances in the plants and/or animals, coupled with clinical signs, clinical and anatomic pathology, is necessary to confirm the diagnosis. When the toxic compound is unknown, the diagnosis is based on epidemiology, clinical signs, clinical and anatomic pathology. Control methods include management practices, biologic control, conditioned food aversion, and integrated control strategies, whereas prophylactic approaches are mainly based on natural or induced resistance and preventive management practices. It is concluded that plant poisonings cause significant economic losses in livestock in South America. However, they are not sufficiently studied in several regions and countries of the continent and the creation of new research groups is necessary to improve the knowledge of poisonous plants.