There are many dangerous and poisonous plants in the world, however these five plants are not only harmful to horses but can be considered extremely lethal.
Hemlock – A multi stemmed weed that causes nervousness,depression and can eventually lead to respiratory failure. There is no treatment for large doses, however if consumed in a small amount animals including horses can recover with supportive care. Geographically this weed is located in mostly grasslands, while the weed does grow in many parts of the world including Asia, Australia and in Idaho.
Water Hemlock – A weed with hairless stems, considered to be one of the most poisonous plants in the United States. The poison is mostly located in the root, when ingested it attacks the nervous system and can cause seizures, heart problems and skeletal issues. While supportive care can help if caught early enough, even horses who survive this weed end up having lasting effects.
Locoweed – A short, colorful weed that looks beautiful with its blueish purple flowers, also known as the crazy weed. It affects the brain cells, and strange behavior is a common side-effect of this weed. The affects are irreversible once ingested, however if a small enough amount is eaten, the horse may recover.
Yew – A woody green shrub with colorful red berries located throughout the western Great Plains area. Common side-effects of ingestion of this shrub include heart and breathing problems and even death. Just a few amount of berries can cause death to a horse within minutes. This is a highly toxic shrub with no treatment for and that will cause.
Red Maple Trees – Eating maple leaves before they wilt is considered to be okay and would do little harm to a horse. However, once they wilt things change for the worse, oxygen can no longer be carried by the blood. Wilted Red Maple Tree Leaves can also cause damage to the liver, kidney and other organs. Even a small amount of leaves can be fatal, and there are very few treatments for the horse once wilted leaves are ingested, however a blood transfusion and an administration of large amounts of intravenous fluids.
While these five plants are some of the most common and deadliest plants to horses, there are many other deadly plants out there including but not limited to Bracken fern, Johnsongrass/Sudan grass, Yellow star thistle/Russian knapweed, Oleander, Tansy ragwort.