We just got a final diagnosis on 3 horses that were showing neurological symptoms similar to EPM.
The toxic plant is called “Singletary Pea“. The seed pods are poisonous and can be ingested from grazing or eaten from baled hay. These horses were eating locally baled round bales that were a grass hay mix of Rye grass, Coastal and some Vetch. The amount of Singletary pea in the hay was enough to make 3 horses very unstable and neurological. Luckily, we caught it and removed the source. All 3 are better but may take 4 to 6 weeks to fully recover. This plant can also affect cattle.
Please share this post so everyone can see what this toxic plant looks like.
When actively growing the seed pods are “hairy” or fuzzy. They produce a small pink or purple flower and have twin leaves that stick up like rabbit ears. This is a picture of what it looks like in the baled hay.
More information from Cornell University – College of Agriculture and Life Sciences:
Department of Animal Science – Plants Poisonous to Livestock:
Scientific Name: Lathyrus spp.
Common Name: Sweet Pea, Tangier Pea, Everlasting Pea, Caley Pea, Singletary Pea
Species Most Often Affected: horses, rodents, turkeys, sheep, humans
Poisonous Parts: seeds
Primary Poisons: DABA, ODAP, amine, phenol, glycoside
Photos and Descriptions from Samuel Roberts Noble Foundation:
This states that cattle and deer can safely eat the plant: Singletary Pea
Alberta Agriculture lists this plant as poisonous:
Sweet Pea, Perennial Pea
Lathyrus odoratus, L. latifolius
Description: Both plants are tall growing vines (2 m) that produce a multitude of flowers in clusters of usually 3 – 5 along their stems. The stems are angular and winged. The sweet pea (L. odoratus), grown as an annual in Alberta, has fragrant flowers in many colours. Seeds are borne in hairy pods. The perennial pea (L. latifolius) is perennial if grown in a protected location. The flowers are rose or white, and the pods are 8 – 12 cm long.
Poisonous Part: Seeds.
Symptoms: Ingestion of large amounts is necessary to induce the following symptoms; prickly sensation, cramps, lameness, paralysis, death. (Internal poisoning: beta-gamma-L-glutamyl-aminopropionitrile in sweet pea and L-alpha, gamma-diaminobutyric acid in perennial pea)
Another good article: Some Weeds are Toxic for Horses
If you are concerned and find this plant on your property you should check with your vet. Be safe and if you have doubts just pull the plants. Some plants are poisonous at different stages of development and some only after drying and, in the case of the Texas horses, baled into their feed.