Sycamore and acorn poisoning in horses

Autumn and its array of colours and tumbling leaves might provide one of nature’s great spectacles but horse owners should also be aware of the dangers of poisoning this season presents, in particularly from sycamore seeds and acorns.

Sycamore poisoning in horses

A toxin called hypoglycin A, which is found in the seeds of sycamore trees, can be fatal if ingested. Vets are not only reminding horse owners to be aware of this but also warning of the fact cases seem to be on the rise.

“Sycamore poisoning”, or atypical myopathy to give it its proper name, is a muscle disease. Symptoms include an animal appearing weak, having difficulty standing, sweating, muscular stiffness, reluctance to walk, muscle tremors and a high heart rate. Although it can be fatal, horses can recover rapidly and well if treated quickly.

Scientists believe cases are on the increase because warm summers seem to encourage sycamore trees to produce more seeds, and because of their famous “helicopters” they can drift a long way.

Spring is another danger time for atypical myopathy, when the seedlings appear and horses may graze on their young leaves.

Acorn poisoning in horses

Another autumnal hazard comes in the form of acorn poisoning. This is less common than sycamore poisoning and less well understood. Signs to look for include lethargy, depression, dehydration, blood in diarrhoea and acorn husks in the droppings.

One of the reasons acorn poisoning is less common is because of the bitter, unpalatable taste of acorns and oak leaves. However, just like with sycamores, warm summers are producing an abundance of seeds but also parched ground where hungry horses might be tempted to graze on things they’d usually avoid.

If your horse or pony displays any symptoms of poisoning or is unwell, consult a vet immediately.

Approved by horse veterinarian Annette Graf, March 2024.

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