If an animal has eaten this plant, the ASPCA Animal Poison Control Center is (888) 426-4435, as printed on the record this page reproduces. A consultation fee may apply.
This page quotes a published document. Everything below in quotation marks is copied word for word from ASPCA Animal Poison Control Center: Brake Fern, published by ASPCA APCC and retrieved on 2026-09-16. The quotations are excerpts; the document itself is linked and is the authority. Nothing has been reworded.
According to the ASPCA Animal Poison Control Center record, Brake Fern (Pteridium aquilinum, family Polypodiaceae) is toxic to horses. Toxic principles: Thiaminase. Clinical signs listed: Poisoning commonly occurs in horses having inadequate forage, or when the plant is incorporated into hay. All parts of the plant are toxic in both green and dry forms. The toxic component causes a thiamine deficiency (an essential nutrient for central nervous system function and metabolism); clinical signs develop after one to two months of chronic ingestion, and can worsen over a two to three day period. Effects include weight loss, incoordination/ excessive staggering (known as "bracken staggers"), the developement of a wide stance with arched back, severe muscle tremors, inability to get up which could lead to serious injury. Death may occur within one to 2 days of onset if not treated. The record was retrieved on 2026-09-16 and is linked below.
The record
- Scientific name
- Pteridium aquilinum
- Family
- Polypodiaceae
- Additional common names
- Braken Fern, Umbewe, Brake, Pasture Bracken, Hog-Pasture Bracken, Eagle fern, Umhlashoshana, Adelaarsvaring
- Toxicity
- Toxic to Horses
- Toxic principles
- Thiaminase
- Clinical signs
- Poisoning commonly occurs in horses having inadequate forage, or when the plant is incorporated into hay. All parts of the plant are toxic in both green and dry forms. The toxic component causes a thiamine deficiency (an essential nutrient for central nervous system function and metabolism); clinical signs develop after one to two months of chronic ingestion, and can worsen over a two to three day period. Effects include weight loss, incoordination/ excessive staggering (known as "bracken staggers"), the developement of a wide stance with arched back, severe muscle tremors, inability to get up which could lead to serious injury. Death may occur within one to 2 days of onset if not treated.
Where this comes from
This is the ASPCA Animal Poison Control Center record for Brake Fern, at https://www.aspca.org/pet-care/aspca-poison-control/toxic-and-non-toxic-plants/brake-fern, retrieved on 2026-09-16. The fields above are the record’s own, shown without change. The ASPCA keeps the record current; the page here is a copy from that date.
This page is information, not a prescription. The right dose for an animal depends on its weight, its age, what else it is taking and what is wrong with it. Those are judgements only the veterinarian who has examined your animal can make. Ring your practice before giving anything.
Sources
- ASPCA Animal Poison Control Center: Brake FernASPCA APCC · retrieved 2026-09-16
“Poisoning commonly occurs in horses having inadequate forage, or when the plant is incorporated into hay. All parts of the plant are toxic in both green and dry forms. The toxic component causes a thiamine deficiency (an essential nutrient for central nervous system function and metabolism); clinical signs develop after one to two months of chronic ingestion, and can worsen over a two to three day period. Effects include weight loss, incoordination/ excessive staggering (known as "bracken staggers"), the developement of a wide stance with arched back, severe muscle tremors, inability to get up which could lead to serious injury. Death may occur within one to 2 days of onset if not treated.” (Clinical Signs)
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