Cliffe Equine's home page
  • Call our surgery01323 815120

Acorn Poisoning

The dangers of Acorn Poisoning 

Extreme warm weather over the summer and the recent high winds and rain has equated to a bumper crop of acorns spread over the countryside.  

Increased risk 

Acorns are known to contain a substance called tannic acid and can cause serious illness if ingested in a sufficient quantity. Horses will not usually favour acorns as a snack due to their bitter taste, however, should their pasture be bare they may ingest acorns as they forage for food. This can be caused by overgrazing or long, hot summers. Some horses are naturally more susceptible to acorn poisoning, with even the smallest amount making them poorly.

The leaves are poisonous too

Many are aware that acorns poise a risk to horses, but often the leaves are overlooked. These contain the same toxicity as acorns and should not be ingested by horses. They should be removed, fenced off or avoided altogether, along with the acorns themselves. 


To prevent acorn/leaf ingestion, avoid using pasture with oak trees present. If unavoidable, manually remove acorns on a daily basis by hand or with a rake. This can be time consuming, so consider fencing off the oak tree including branch span to avoid grazing in that area.  Ensure supplementary feed is provided if forage is low, to avoid temptation to snack on acorns. 

Signs of acorn poisoning

  • Husks in droppings 
  • Dull appearance/Depression/lethargy 
  • Colic symptoms 
  • Dehydration 
  • Loss/reduced of appetite 
  • Increased lying down 
  • Mouth ulcers 
  • Constipation (with blood present) 
  • Diarrhea  


Unfortunately, there is no specific treatment for tannic poisoning. Care given will depend on severity of the symptoms and the stage of the illness but often includes pain relief, activated charcoal, electrolytes and fluids. 

Acorn poisoning can be fatal, and we'd advise anyone that suspects their horse of having it to call their veterinarian immediately. As always, early intervention is imperative for a positive prognosis. 

Remember: If you have any concerns or questions regarding Acorn Poisoning, please don’t hesitate to ring the team on 01323 815120 or email