Brake Fern Toxic?

Updated 2026-03-06| 3 min read| 1,754 found this helpful

All plant parts are toxic to horses in both fresh and dried forms, while toxicity to cats and dogs is unconfirmed.

Thiaminase, the primary toxic compound, causes thiamine deficiency leading to neurological symptoms like staggering after chronic ingestion.

Long-term exposure causes chronic cystitis, enzootic hematuria in ruminants, and progressive retinal atrophy in sheep.

FAQ

Is Brake Fern toxic to Humans?

Limited acute toxicity data is available; long-term consumption is linked to elevated cancer risk, while acute ingestion may cause mild gastrointestinal distress. (Moderate)

Is Brake Fern toxic to Cats?

No confirmed toxicity data available; monitor for lethargy, vomiting or appetite loss if ingestion is suspected. (Unknown)

Is Brake Fern toxic to Dogs?

No confirmed toxicity data available; monitor for lethargy, vomiting or appetite loss if ingestion is suspected. (Unknown)

Is Brake Fern toxic to Horses?

Weight loss, incoordination (bracken staggers), wide stance with arched back, severe muscle tremors, inability to stand, potential death within 1-2 days of symptom onset if untreated. (Severe)

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

Toxicity Details

Humans

Moderate

Limited acute toxicity data is available; long-term consumption is linked to elevated cancer risk, while acute ingestion may cause mild gastrointestinal distress.

Cats

Unknown

No confirmed toxicity data available; monitor for lethargy, vomiting or appetite loss if ingestion is suspected.

Dogs

Unknown

No confirmed toxicity data available; monitor for lethargy, vomiting or appetite loss if ingestion is suspected.

Horses

Severe

Weight loss, incoordination (bracken staggers), wide stance with arched back, severe muscle tremors, inability to stand, potential death within 1-2 days of symptom onset if untreated.

Toxicity Snapshot

Toxic PartsWhole plant; above-ground parts remain toxic after drying; highest toxic compound concentration is in young growing plant parts.

Exposure RouteIngestion is the only confirmed exposure route; no dermal or inhalation toxicity has been reported.

Toxic CompoundsThiaminase; Caffeic acid; Astralagin; Isoquercetin; Ptaquiloside (PTA); Pterosin B (PTB)

First Aid & Prevention

First 30 Minutes

• Remove all Brake Fern material from the animal's access immediately to stop further exposure.
• Collect a sample of the ingested plant for accurate identification by veterinary professionals.
• If ingestion occurred within 2 hours, induce vomiting in non-ruminants only under explicit veterinary guidance.

Contact Vet Immediately

• Any suspected ingestion of Brake Fern by horses, ruminants or pigs.
• Observation of neurological symptoms including staggering, muscle tremors, or inability to stand.
• Signs of bleeding, pale mucous membranes, or unexplained weight loss in grazing animals.

Prevention

• Inspect pastures regularly and remove all Brake Fern growth to prevent accidental ingestion by livestock.
• Verify hay supplies are free of Brake Fern contamination, especially for horse feed rations.
• Provide adequate high-quality forage to horses to discourage consumption of toxic weed species.

Treatment & Prognosis

• Administer thiamine (vitamin B1) to non-ruminants: 100-200mg twice daily for horses on day 1, then once daily for 7-14 days as prescribed.
• Provide repeated blood transfusions (minimum 4-5L) and iron-dextran supplements for affected cattle per veterinary direction.
• Deliver supportive care including fluid therapy and pain management based on individual presenting symptoms.

Emergency? Open PlantFun for real-time AI guidanceGet App

Professional Toxicology

Scientific NamePteridium aquilinum

AliasesBracken Fern、Umbewe、Brake、Pasture Bracken、Hog-Pasture Bracken、Eagle fern、Umhlashoshana、Adelaarsvaring、Adlerfarn、Fougère aigle、Felce aquilina

Toxicity Grade

HumansModerate

CatsUnknown

DogsUnknown

HorsesSevere

Target Organs

Central nervous systemBone marrowRetinaBladderBlood vesselsKidneys

Mechanism of Action

• Thiaminase breaks down thiamine (vitamin B1) in the body, causing deficiency that impairs central nervous system function and metabolism.

• Ptaquiloside converts to a reactive alkylating dienone in alkaline environments, causing DNA damage and chronic organ injury.

• Toxic compounds damage bone marrow, increase capillary fragility, and impair blood clotting function in ruminants and rabbits.

Other Species Risk (CliniTox)

Information from CliniTox veterinary text.

Cattle/Ruminants: Chronic ingestion causes chronic cystitis, bovine enzootic hematuria, bone marrow damage, bleeding disorders, and increased capillary fragility.

Sheep: May develop progressive retinal atrophy (bright blindness) due to blood vessel stenosis, plus thiamine deficiency with chronic exposure.

Pigs: Primarily develop thiamine deficiency after ingestion, leading to neurological impairment and coordination issues.

Rabbits: Exposure causes bone marrow damage, bleeding disorders, and increased capillary fragility.

Confusion Risk

The following plants look similar and may be confused:

Other toxic fern species Various Polypodiaceae family species

Many fern species share similar frond morphology; Brake Fern can be distinguished by its large, triangular, multi-branched fronds, and all unidentified ferns should be treated as potentially toxic for livestock.

Use PlantFun to scan and avoid misidentificationGet App

Related Toxic Plants

Male Fern

Dryopteris filix-mas

High toxicity; may cause severe gastrointestinal distress and neurological damage if ingested.

Common Polypody

Polypodium vulgare

Moderate toxicity; contains thiaminase and irritant compounds that cause digestive upset.

Cretan Brake Fern

Pteris cretica

Low to moderate toxicity; causes mild gastrointestinal irritation if consumed in large quantities.

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

2. CliniTox (Universität Zürich)

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