Loco Weed Toxic?

Updated 2026-03-06| 4 min read| 3,315 found this helpful

Astragalus spp.

Toxicity to horses is confirmed, while toxicity risks for cats, dogs and humans have not been formally verified

The primary toxic principle identified by ASPCA is the indolizidine alkaloid swainsonine

Exposure in horses can cause neurological impairment, digestive disruption, and severe reproductive harm including fetal death and birth defects

FAQ

Is Loco Weed toxic to Humans?

No confirmed toxicity or symptom data available for human exposure (Unknown)

Is Loco Weed toxic to Cats?

Toxicity status unknown, no verified clinical symptom records available (Unknown)

Is Loco Weed toxic to Dogs?

Toxicity status unknown, no verified clinical symptom records available (Unknown)

Is Loco Weed toxic to Horses?

Incoordination, depression, inability to eat and drink, fetal death, birth defects (Moderate)

Not sure which plant? Snap a photo to ID in 1 secondGet App

Toxicity Details

Humans

Unknown

No confirmed toxicity or symptom data available for human exposure

Cats

Unknown

Toxicity status unknown, no verified clinical symptom records available

Dogs

Unknown

Toxicity status unknown, no verified clinical symptom records available

Horses

Moderate

Incoordination, depression, inability to eat and drink, fetal death, birth defects

Toxicity Snapshot

Toxic PartsAll above-ground plant tissues (leaves, stems, flowers, seeds) are toxic, including dried, dead plant material

Exposure RouteIngestion is the only confirmed exposure route for toxicity

Toxic CompoundsSwainsonine

First Aid & Prevention

First 30 Minutes

• Immediately remove the affected animal from areas with locoweed access to stop further ingestion
• Collect any remaining ingested plant sample for official identification confirmation
• Monitor for early signs of incoordination or behavioral changes while arranging veterinary care

Contact Vet Immediately

• Any confirmed or suspected locoweed ingestion in horses
• Observation of unexplained incoordination, depression, or refusal to eat/drink in animals with access to locoweed
• Pregnant animals that may have ingested locoweed to assess reproductive risk

Prevention

• Inspect grazing pastures regularly for locoweed growth and fully remove all identified plants including roots
• Provide sufficient high-quality forage for grazing animals to reduce risk of accidental locoweed consumption
• Screen hay supplies for locoweed contamination before feeding to horses or other livestock

Treatment & Prognosis

• Administer supportive care to correct hydration and nutrition deficits for animals unable to eat or drink independently
• Provide symptomatic management for neurological signs under direction of a licensed veterinarian
• Conduct long-term monitoring of pregnant exposed animals for reproductive complications including fetal loss or congenital defects

Emergency? Open PlantFun for real-time AI guidanceGet App

Professional Toxicology

Scientific NameAstragalus spp.

AliasesLocoweed

Toxicity Grade

HumansUnknown

CatsUnknown

DogsUnknown

HorsesModerate

Target Organs

Nervous systemReproductive systemDigestive systemLiver

Mechanism of Action

• Swainsonine inhibits the function of the cellular alpha-mannosidase enzyme, leading to toxic accumulation of unprocessed glycoproteins in cells across multiple organ systems

Other Species Risk (CliniTox)

Information from CliniTox veterinary text.

Cattle: Documented to be susceptible to swainsonine toxicity from locoweed ingestion, with similar neurological and reproductive symptoms as seen in horses

Sheep: Low recorded susceptibility to locoweed toxicity, requiring much higher exposure doses to develop clinical signs compared to horses or cattle

Confusion Risk

The following plants look similar and may be confused:

Alfalfa Medicago sativa

Both are Fabaceae plants with similar trifoliate leaf structure; locoweed produces elongated racemes of pealike flowers, while alfalfa has shorter clusters of typically purple flowers

White Clover Trifolium repens

Both have trifoliate leaves; locoweed leaves are longer and narrower than rounded clover leaflets, and do not produce clover's characteristic round white flower heads

Use PlantFun to scan and avoid misidentificationGet App

Related Toxic Plants

Black Locust

Robinia pseudoacacia

Download PlantFun App

Identify, grow and care for plants effectively!

Instant Plant ID

Take a photo to quickly identify plants.

Smart Care Reminders

Generate watering and care schedules.

Toxicity & Disease Diagnosis

Identify toxic plants and pests with treatment advice.

Data Sources

1. ASPCA Animal Poison Control

This information is for reference only and does not constitute medical advice. If ingestion or poisoning is suspected, seek medical or veterinary attention immediately.

View Full Plant Wiki