VETS in Dorset are warning horse owners to beware of the potentially fatal effects of sycamore seeds this autumn.

Sycamore seeds are toxic and can cause Seasonal Pasture Myopathy (SPM), which was previously known as Atypical Myopathy (AM), a fatal muscle disease.

British Veterinary Association president Sean Wensley said: “SPM is a disease that is extremely distressing for both the animal and the owner of the horse affected. BVA is working closely with our colleagues in BEVA, who deal with the aftermath of sycamore poisoning in horses all too often throughout the autumn, to ensure we get timely advice to owners to prevent their animals suffering in this way.”

Horses that develop SPM are usually kept in sparse pastures with an accumulation of dead leaves, dead wood and trees in or around the pasture and are often not fed any supplementary hay or feed. While the seeds may not be directly palatable, horses grazing on poor quality pasture may ingest considerable numbers of them.

Owners are advised to restrict access to seeds by using temporary fencing, ensure horses have access to good quality uncontaminated pasture, move horses off pasture at times of risk, provide supplementary feed and avoid leaving wet hay on the ground where it will rot and could trap seeds.

A field without sycamore trees can still contain seeds spread by high winds or flood water. It is not advised to prune trees as this can lead to pasture contamination and increase the risk to horses.