BEVA Warns of Threat from Sycamore Contamination

12 June 2023

The British Equine Veterinary Association (BEVA) has raised alarm bells as horse vets round the UK have become increasingly concerned about farmers producing hay containing sycamore seeds and saplings. This contamination poses a risk to any horses consuming the hay and can lead to atypical myopathy, a disease that is fatal in 75% of cases.

Sycamore trees produce a toxin called Hypoglycin A and when this is eaten by horses, it causes severe muscle damage with typical symptoms being general weakness and an inability to stand. Horses often die within 24 hours of the onset of symptoms.

The warm spring and hot summer of 2022 allowed for a good production of seeds by sycamore trees, and these are now germinating, leading to an unusually large increase in seedlings this year. This has resulted in a rise in cases of atypical myopathy.

Whilat may horse and yard owners are aware of the dangers, and actively clear Sycamores and saplings from their land, many do not consider the risks that may occur from other forage brought on to the yard such as hay or haylage provided by third party suppliers.

The most common time of year for vets to see atypical myopathy is autumn when horses on sparse grazing may be affected, having eaten the seeds, but due to the large number of seeds produced last year, there are currently more seedlings than usual present on grazing land and this has produced a rise in early cases.

Unfortunately, the seeds and seedlings still pose a threat to horses when dry and consumed in hay and, with haymaking now under way, BEVA is urging farmers to be vigilant, even in fields with no sycamore trees, as the seeds can travel hundreds of metres from the parent tree. If saplings are spotted in hay fields, whether dead or alive, they should be removed prior to cutting for hay.

BEVA president David Rendle said: “By raising awareness of the risks of contaminated hay being fed to horses, BEVA is hoping farmers will be able to identify any sycamore saplings within the crop while the grass length enables them to be seen.

“We are urging farmers to check their fields now and to discuss the risks from sycamores with their local equine veterinary practice if they need any further advice.”

If you are concerned about any hay you have purchased, or your horse’s welfare, speak to your local vet or hay supplier. For more information, visit

You can also find out more information about Atypical Myopahy, HGA Testing and grazing management, -as well as all other aspects of practical an administrative yard management- on the Yard Owner Hub: Equine Ailments Guidance for Livery Yards and Equestrian Industry | Livery List Hub (

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