Are acorns poisonous to horses?
The Natural Way - specialised in itching and skin complaints and the natural treatment of sweet itch, mud fever and CPL.
If your horse eats acorns, you may wonder whether they are poisonous or harmless.
Herd of Konik horses eating acorns in the forest © Laura Cleirens
Why do horses eat acorns?
Acorns, oak leaves and bark contain an average of 7-9% tannin or tannic acid, with unripe acorns and green leaves being particularly rich in this substance. The more tannin, the more bitter the taste. Acorns also contain all 8 essential amino acids, carbohydrates, proteins and fatty acids.
When the leaves and fruits fall in autumn and access to grass becomes more limited, horses may also start to eat acorns.
To a certain extent, this is not a problem.
Fortunately, acorns have a bitter taste, which means that horses do not always find them very palatable. The brown, ripe acorns are eaten in particular, and this also has advantages, e.g. a vermifuge effect.
I recently observed a herd of Konik horses eating acorns together for about fifteen minutes, and then moving on, feeding on grass, blackberries and bark.
Acorn poisoning?
However, a horse can suffer from acorn poisoning. Horses that are suddenly exposed to acorns, eat large quantities, horses with questionable health and young horses are particularly susceptible to this.
Symptoms of acorn poisoning in horses include colic, pain in the abdomen and flanks, drowsiness, reduced appetite, kidney problems, diarrhoea and dark, coffee-coloured urine.
Be sure to consult your vet if these symptoms are present and/or you suspect acorn poisoning.
Are acorns poisonous to horses? © The Natural Way - Laura Cleirens
Management tips
Do you have oak trees in your pasture or paddock and are you unsure what to do? Here are a few management tips as a precaution:
- Provide sufficient roughage (hay, grass, branches, herbs, etc.)
- Always provide fresh drinking water (without acorns or leaves)
- Sweep up acorns and remove them from the paddock
- Use strip grazing or fencing
Common sense
Some horses stand under an oak tree for 20 years, eating from it and suffering no ill effects. Use your common sense and monitor your horse's health, but don't be afraid to roll up your sleeves and fence off part of the paddock when necessary if things get out of hand. Better safe than sorry.
Clearing acorns is a real chore, but don't panic immediately when you see your horse munching on a pile of acorns. There is no right or wrong, but as with everything: moderation is key.
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Laura Cleirens from The Natural Way specialises in the natural treatment of itching and skin complaints in horses, such as sweet itch, mud fever and CPL.
Discover our 100 % natural range here: Sweet Itch Lotion, Mud Fever Oil, CPL Oil, Nature Shampoo and Zoem Spray, as well as e-books on Primal Food, Itch and Horse Herbs.
© Laura Cleirens: 2025.10.14
Last update: 2026.01.28
