Understanding Bracken Poisoning In Horses

Horses can be attracted to bracken ferns when the area they graze in doesn't provide sufficient edible plants, and, unfortunately, some horses simply develop a taste for them even when they have a lush grazing pasture available to them. Bracken contains the enzyme thiamase, which is toxic to horses and breaks down vitamin B1 in your horse's body. Horses need this vitamin to maintain healthy cellular respiration, and without sufficient vitamin B1, your horse will develop neurological problems. Here's what you need to know about bracken poisoning in horses:


Early symptoms of bracken poisoning include muscle spasms and tremors, a decline in co-ordination, nervousness and spending an increasing amount of time lying down. As the condition progresses, your horse can experience lethargy, seizures, sight loss and death. Prompt treatment is vital to give your horse the best chance of recovering from bracken poisoning. Even if you remove your horse from a grazing area containing bracken, they should be seen by a vet, as thiamase can remain in your horse's system and damage their health for some time after bracken has been consumed.

Diagnosis And Treatment

There are no specific tests that can confirm your horse is suffering from thiamase toxicity, so your vet will diagnose bracken poisoning by assessing your horse's symptoms and taking into consideration what's known about the presence of bracken in your local area. To treat bracken poisoning, your vet will prescribe vitamin B1 supplements until symptoms improve. This neutralises the effect of thiamase and gives your horse's body the opportunity to recover. Treatment generally takes a couple of weeks if it's started soon after your horse shows symptoms.

Recognising Bracken Ferns

You can help keep your horse safe from bracken poisoning by learning how to identify it. In spring, bracken fronds, which are the leave-like part of a fern, appear as tight coils, and these coils gradually unfurl as temperatures increase. Each fern is spilt into three, and the bright green fronds have a triangular appearance. Bracken continues to grow until late summer and can reach over a metre in height. In autumn, the fronds begin to wither and turn brown, and by winter, they have died back to ground level.

Early intervention can prevent unnecessary suffering and save your horse's life. Make sure to promptly seek the help of a vet clinic if you're concerned about the health and welfare of any animal in your care.