Toxicity

Horsetail toxicosis in horses is a rare but potentially life-threatening condition caused by repeated consumption of horsetail plants, most often through contaminated hay. Early signs such as weight loss, weakness, and mild incoordination may be subtle, making a history of...

Fiddleneck toxicosis in horses is a form of plant poisoning caused by pyrrolizidine alkaloids found in species of fiddleneck plants in the genus Amsinckia. Horses may ingest the plant while grazing or consume its dried material and seeds in contaminated...

Hoary alyssum toxicosis in horses is a potentially serious condition caused by eating fresh or dried hoary alyssum (Berteroa incana). Equine exposure often occurs through contaminated hay, where the weed is more difficult to recognize after harvesting and baling. Affected...

Heliotrope toxicosis in horses is a potentially fatal form of plant poisoning caused by toxic pyrrolizidine alkaloids that damage the liver. Because these compounds have cumulative effects, repeated consumption of small amounts may cause serious injury before a horse shows...

Jimsonweed poisoning in horses is a potentially life-threatening toxicosis caused by ingesting Datura stramonium, an invasive plant containing potent tropane alkaloids. These compounds disrupt normal nerve signaling and can severely impair gastrointestinal function. Exposure is difficult to detect when jimsonweed...

Laurel toxicosis in horses is an uncommon but potentially serious poisoning caused by ingesting toxic Kalmia shrubs, including mountain laurel and sheep laurel. All parts of these plants can contain grayanotoxins, which disrupt normal nerve, muscle, and heart function. Horses...

Horse chestnut toxicosis in horses is an uncommon but potentially serious poisoning caused by ingesting seeds or other parts of trees in the Aesculus genus. Fallen seeds, young shoots, leaves, bark, and flowers can all contain toxic compounds that affect...

Foxglove poisoning in horses is a potentially fatal emergency caused by ingesting Digitalis purpurea, a toxic ornamental plant that can severely disrupt heart function. Although cases are uncommon, foxglove sometimes grows near pastures and paddocks or ends up in contaminated...

Cycad toxicosis in horses is a potentially fatal poisoning caused by ingesting cycads, a group of palm-like ornamental plants that includes the sago palm. Although exposure is uncommon, these plants may be found near paddocks, barns, gardens, and landscaped properties,...

Fetterbush toxicosis in horses is an uncommon but potentially serious form of plant poisoning caused by ingesting shrubs from the Leucothoe genus and related species. These plants may be found in wooded environments or used in landscaping around farms and...

English ivy toxicosis in horses occurs when horses consume the leaves, vines, or berries of this common ornamental plant. Although its bitter taste typically discourages horses from eating large amounts, exposure can occur along overgrown fence lines, in wooded paddocks...

Day blooming jasmine toxicosis in horses is a progressive form of poisoning caused by repeated ingestion of the ornamental shrub Cestrum diurnum. The plant grows in tropical and subtropical regions and may be found in landscaped areas, along fence lines,...

Death camas toxicosis in horses is an uncommon but potentially life-threatening form of plant poisoning caused by ingesting death camas. These highly toxic plants grow across much of North America and may be consumed when pasture forage is sparse or...

Desert rose toxicosis in horses is an uncommon but potentially life-threatening poisoning caused by ingesting Adenium obesum, a succulent ornamental plant. Unlike many toxic pasture weeds, desert rose is typically found in landscaped gardens, container plantings, and discarded yard waste....

Ibuprofen toxicity in horses is a serious risk because this common human pain medication is not approved or recommended for equine use. Although ibuprofen is widely available over the counter and commonly used in people for pain, inflammation, and fever,...

Castor bean (Ricinus communis) is a highly toxic flowering plant that can pose a serious poisoning risk to horses, especially when seeds are chewed or crushed.The plant is widely distributed throughout tropical, subtropical, and warm temperate regions worldwide. Castor bean...

Black locust (Robinia pseudoacacia), often incorrectly referred to as acacia, is a deciduous tree in the bean family (Fabaceae) that can pose a toxic risk to horses. Native to parts of eastern North America, black locust grows rapidly and spreads...

Avocado toxicity in horses occurs when horses ingest leaves, fruit, stems, bark, or seeds from the avocado tree (Persea americana). Although avocado fruit is commonly consumed by humans, the plant contains compounds that can cause illness in several animal species,...

Cannabis sativa poisoning in horses is uncommon, but increasing cannabis cultivation and product availability have made accidental exposure more likely for horses. Cannabis sativa is an annual herbaceous plant in the Cannabaceae family with a long history of industrial, medicinal,...

Allium plants are a bulb-forming species that include onions, garlic, leeks, shallots, and chives. Although these plants are common in human diets, they can pose a toxic risk to horses when consumed in sufficient amounts or repeatedly over time. Exposure...

Autumn crocus (Colchicum autumnale), also known as meadow saffron, is a highly toxic plant that can pose a serious risk to horses in pastures, hay fields, and contaminated forage. This small herbaceous perennial is native to Europe and parts of...

Bracken fern (Pteridium aquilinum) is a widespread toxic plant that can pose a serious risk to horses when consumed repeatedly in pasture or contaminated hay. This adaptable perennial fern grows throughout North America and many other regions, often establishing dense...

Blue-green algae poisoning in horses is a serious and potentially fatal toxicosis caused by cyanobacteria, microscopic aquatic organisms that can produce potent toxins in contaminated water sources. Harmful cyanobacterial blooms occur worldwide in freshwater and brackish water systems. Under favorable...

Caffeine toxicity in horses is an uncommon but important condition that can occur when horses are exposed to coffee by-products, cocoa materials, or contaminated feed. While caffeine is widely recognized as a stimulant in humans, its effects in horses have...

Non-steroidal anti-inflammatory drugs (NSAIDs) are a type of medication used to reduce inflammation and treat pain in horses. In equine medicine, NSAIDs are commonly used in supportive care for a wide range of symptoms and conditions such as colic, pain,...

Ionophores are compounds commonly used as additives in feeds for cattle, poultry, and other commercially raised animals. While these compounds are beneficial for certain animals, horses metabolize ionophores differently, making them susceptible to negative effects if exposed to toxic doses....

Cyanide toxicosis is a potentially fatal condition in horses which is caused by the ingestion of plants containing cyanogenic glycosides. Understanding cyanide toxicosis is essential for anyone involved in horse care. Over 3,000 plants worldwide are known to produce cyanogenic...

Nitrogen compounds, crucial for fertilizers, have revolutionized agriculture, ensuring food security but they pose environmental risks such as water pollution and algae blooms. Horses, while less susceptible than ruminants to nitrate poisoning due to their digestive system, can suffer severe...

Ryegrass is a popular forage choice worldwide, and is a nutritious source of protein and energy for horses and other grazing animals. Although both species of ryegrass are good sources of nutrition and are not toxic in and of themselves,...

Atypical Myopathy (AM) and Seasonal Pasture Myopathy (SPM) are highly fatal muscle disorders in horses caused by the ingestion of seeds of the box elder or sycamore trees. Seeds of these species contain a compound called hypoglycin A that converts...