Recognising the Symptoms of Acorn Poisoning in Horses

Acorn poisoning can be a serious and sometimes life-threatening condition for horses, especially during autumn when oak trees shed large quantities of acorns. While some horses may show little interest, others find them quite palatable — and even a small amount can cause significant health issues.

What causes acorn poisoning?

Acorns, oak leaves, and bark all contain tannins, which can be toxic when consumed in excess. These toxins irritate the digestive system and can cause damage to the kidneys and liver. The level of toxicity depends on the horse’s size, the amount eaten, and the concentration of tannins in the acorns, which can vary year to year.

Symptoms to watch for:

• Loss of appetite or reluctance to eat

• Colic symptoms, such as pawing, rolling, or restlessness

• Diarrhoea, often dark or containing blood

• Depression or lethargy

• Swelling around the legs or underside

• Signs of dehydration (such as dry gums or reduced urination)

• In severe cases, collapse or signs of kidney failure

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If you suspect your horse has eaten acorns and shows any of these symptoms, it’s important to contact your vet immediately. Early intervention can make a significant difference to recovery.

Prevention tips:

The best prevention is to limit access to oak trees during the autumn months. Regularly check fields for fallen acorns and remove them where possible. Providing plenty of forage can also help reduce the temptation for horses to eat acorns out of curiosity or hunger.

At our centre, we always emphasise proactive management and owner education — understanding risks like acorn poisoning helps ensure your horse stays safe, healthy, and performing at their best throughout the year.