Autumn colours herald start of deadly Seasonal Pasture Myopathy season

A Sycamore Maple (Acer pseudoplatanus) in Germany. Photo: Willow (Own work) CC BY-SA 3.0 via Wikimedia Commons
A Sycamore Maple (Acer pseudoplatanus) in Germany. Photo: Willow  CC BY-SA 3.0 via Wikimedia Commons

As autumn approaches the northern hemisphere trees are displaying their seeds, and veterinarians are warning horse owners to beware of the risks of any sycamore trees on or near their grazing.

Sycamore seeds are toxic and can cause the fatal disease Seasonal Pasture Myopathy (SPM) (also referred to as Atypical Myopathy). SPM is a highly fatal muscle disease in horses caused by the toxin hypoglycin A, which is contained in tree seeds including that of the sycamore. While sycamore seeds may not be directly palatable to horses, those grazing on poor quality pasture may ingest considerable numbers of them.

Owners are advised to minimise the risk of their horses eating sycamore seeds or leaves.
Owners are advised to minimise the risk of their horses eating sycamore seeds or leaves.

Horses kept in sparse pastures with an accumulation of dead sycamore leaves, dead wood and trees in or around the pasture and without access to supplementary hay or feed, are the most susceptible.

The British Equine Veterinary Association (BEVA) has advised several steps that should be taken to prevent sycamore seeds falling where they are in reach of horses.

·      Ideally move horses off pasture at times of risk.

·      Restrict access to seeds by using temporary fencing.

·      Ensure horses have access to good quality uncontaminated pasture.

·      Provide consistent access to clean, palatable hay or haylage to minimise the risk of horses being tempted to ingest seeds.

·      Do not fell trees, since doing so can lead to massive pasture contamination, further increasing the risks to horses

·      Discuss the risks and how to identify early clinical signs of SPM with your veterinarian

·      Be aware that a field without sycamore trees can still contain seeds spread by high winds or flood water.

Mark Bowen, Senior Vice President of BEVA said: “Please plan ahead and take steps now to prevent the risk of your horse contracting Seasonal Pasture Myopathy. It’s a devastating condition that can frequently be fatal despite treatment. If you are worried about the safety of your grazing speak to your veterinary practice for advice.”

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