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Oak toxicosis and atypical myopathy horses

High winds and a higher risk of atypical myopathy

06 October 2025

Storm Amy made quite a mark over the weekend. We hope your horses stayed safe and well. Whilst there has been some obvious damage with fallen trees and branches, please check your fields thoroughly if you haven't already.

Sections of fencing may need to be repaired to keep horses contained and to reduce the risk or injury. Unwanted, possibly even toxic, seeds may have blown in to fields - even if there are no large trees close by. 

Sycamore seeds, leaves and seedlings can all contain the deadly toxin Hypoglycin- A (HGA), which can cause atypical myopathy. An often fatal condition. It is crucial that fields are checked thoroughly. 

Acorns too can be very problematic for horses, with the potential to cause damage to the kidneys and the Gastro-Intestinal (GI) tract. 

Horses will tend to avoid eating toxic plants, but we should not rely on them to do so. Where there is little to eat horses are far more likely to consume things they shouldn't. Foals and youngstock are likely to experiment with new tastes and textures. Some horses actually can have quite a taste for them!

The Blue Cross UK have some sensible advice for minimising the risks of atypical myopathy - most of which is also applicable to reducing the risk of oak toxicosis. Please find the page link here. The relevant advice is toward the bottom of the page.

The advice includes feeding forage away from the floor. This can be hay in nets, hay or alternative forage placed on top of mud control matting or hardstanding, and soaked pelleted forages or dampened chops / chaffs in the feed bowl. For those with good teeth for chewing, Simple System Brix can be a very convenient way of feeding a substantial (1kg) portion of forage.

Should you need feeding advice, contact Simple System's Feed Line on 01728 604 008 or by email to info@simplesystem.co.uk. If you suspect your horse has atypical myopathy or oak toxicosis do not hesitate to seek veterinary advice.

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