- Colic
- Diarrhoea (often dark and foul-smelling)
- Lethargy
- Kidney damage in severe cases
In a mast year like we are having in 2025, there’s a bumper crop of all kinds of nuts and fruit. When this coincides with a period of limited grass growth – think how dry this summer has been – it results in animals being more likely to seek out and eat things outside their normal diet. Unfortunately, acorns are in particular abundance, and if consumed in excess, they can be fatal. This is something we are seeing in both our Farm and Equine practices.
Acorns and oak leaves contain high levels of tannins. When horses metabolise these compounds, they form by-products that bind to proteins in cell membranes, damaging and altering their function. This leads to severe inflammation of the gut and kidneys, resulting in diarrhoea, dehydration, and potentially organ failure.
The number of acorn poisoning cases varies from year to year – similar to atypical myopathy – likely due to environmental factors that we don’t yet fully understand. However this year has been particularly bad with a number of factors as explained above combining. As owners we need to remain vigilant and try our best to protect our horses.
✅ Provide ample forage to reduce grazing on risky plants
✅ Check paddocks regularly and remove fallen acorns
