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Maple poisoning kills horses in Denmark 

Photo: Canva Pro

The veterinarian and co-owner of a vet clinic in southern Denmark said that maple poisoning should be taken seriously, and as a consequence of climate change, we may see more poisonings in the future. 

About veterinarian Xenia Lund Jensen   

Xenia Lund Jensen is a veterinarian at the University of Copenhagen specialising in equine behaviour. Xenia has had a horse for many years and rides western and trails.

The deadly maple 

The maple tree is toxic to horses due to the substance hypoglycin-A, which is found in both seeds and leaves. The seeds are characterized by having small wings that create a helicopter-like motion when they fall from the tree - and potentially fly into paddocks - typically in autumn. Maples can be found pretty much everywhere.  

Normally, maple poisoning is most common in autumn, but the weather hasn't been quite within the norm this year, says chief veterinarian Xenia Lund Jensen. She tells us about a case she was called out to on Lolland, in southern Denmark: 

" I was recently called to a property on Lolland with several seriously ill horses, where all horses ended up being euthanized due to severe maple poisoning. There was a dialogue with the referral hospital regarding hospitalization, but due to the severe muscle cramps and symptoms of poisoning, transporting the horses was not safe. The horses were treated intensively in the stables, but they could not be saved." 

Symptoms of maple poisoning 

  • Colic  
  • Sore, stiff muscles  
  • Low mood  
  • Breathing problems   
  • Port-coloured urine (myoglobinuria)  
  • Cardiac arrhythmia (heart rhythm disturbances)   
  • Coma resulting in death 

The chief veterinarian emphasizes: "It's important when you experience colic - especially if it's the case with more than one horse in the stable - that you contact your vet immediately. You should not wait for recovery by walking the horse. The horse must be seen as soon as possible and given fluids to dilute the toxin in the hope of saving the horse's life." 

If the poisoning is detected early enough, the horse can be treated for colic and saved. That's why it's important to contact your vet as soon as you detect symptoms. But the most important thing is to try to avoid the poisoning in the first place. 

Photo: Canva Pro

The entire herd had to be euthanized 

The concerned vet tells us about the specific case on Lolland in Denmark:  

"There were maple trees near the horses' paddocks. But the horses had been in this paddock all their lives and there have been horses on the property for over 20 years without any problems. I was called out to a colicky horse and on arrival another horse suddenly became colicky. They had port-colored urine and convulsive colic. Treatment was administered, but very quickly it became apparent that it was poisoning as the horses became seriously ill. Unfortunately, both horses died despite intensive treatment." 

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"It was a terrible experience for the owner, who had to say goodbye to all her horses within 24 hours",
says the vet. 

Horses can be tested for maple poisoning through a blood sample, which must be sent to a laboratory for results. The test result is rarely enough to save the horse if the symptoms are not detected in time, but it can establish the presence of maple poisoning in horses within the area and country. From the specific situation on Lolland, veterinarian Xenia Lund Jensen says: 

"Blood samples were sent to a laboratory with very high levels of the toxin hypoglycin A. There was plenty of grass in the paddock and the horses had a large area to walk on, so why the horses had ingested the toxic plants is unknown." 

As treatment for maple poisoning is not 100% successful, you should try to avoid the trees spreading seeds in the paddock "It's important to review your paddocks and even if the horse has never shown interest in ferns, meadowsweet, yew, maple, oak or similar, the weather can change and so can the horses. These plants need to be removed." 

Climate Change 

Our actions on Earth can have far-reaching consequences. They can cause maple seeds to be found in many more places in the grass than usual. Due to longer and warmer droughts last summer, maple trees had ample opportunity to shed many seeds. The wet period this year provides the seeds with optimal conditions for germination this spring. This means that maple seeds can be everywhere in the grass.  

"The sprouts can easily get in when the horse eats the delicious spring grass." 

the vet emphasizes.

So even if you don't think your horse is used to eating maple seeds, it can still be a good idea to avoid the risk of your horse ingesting the seeds by moving/removing the trees or moving the paddock. 


This is the time of year when you should pay attention to the following: 

  • Check your paddocks for poisonous plants and trees  
  • Have a chat about poisonous plants and trees in the stable  
  • Make other horse owners aware of (maple) poisoning, which is extremely serious for horses  
  • If in doubt, talk to your vet, they can help with advice and guidance 

And maybe we should all do a little extra to avoid climate change - also for the sake of our horses.


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