Poisonous, or toxic, plants contain compounds that may cause death, reproductive problems, birth defects, neurological, digestive, or physiological disorders in livestock. Poisonous plants are a major economic loss to the livestock industry every year, and can affect three to five percent of cattle, sheep, goats, and horses (Panter et al., 2011). In 1991, poisonous plants caused an estimated $340 million in losses, which is equivalent to approximately $580 million in 2020 (James et al., 2011 and Frisvold, 2020). Locoweed poisoning alone is estimated to cause $100 million in losses annually (Cook et al., 2009). The economic impact of poisonous plants of livestock can both direct and indirect losses (Panter et al., 2011). Direct losses are effects on animals and include death, abortions, birth defects, decreased fertility, and decreased organ function. Indirect losses are management costs and include increased medical treatments, decreased land values, lost time to increased management, and increased feed requirements.
These toxins in vegetation are often called secondary compounds and are made by plants in response to grazing, microbes, other plants (allelopathy), or environmental stresses. Poisonous plants are grouped according to their primary type of poison. The more common types of poisons include:
- Alkaloids
- Glycosides
- Minerals
- Organic acids
- Phytotoxins
- Resins
- Miscellaneous unknown poisons
Identifying poisonous plants is complex due to environmental interactions. Growth state, ecological site, weather, and plant part can all modify toxicity and are all species specific. Aside from environmental issues, animal factors also add to the complexity. Age, experience, body condition, diet selection, and kind/class of animal also play a role in the presence and magnitude of poisoning.