20/10/2025
I’m just sharing this because someone recently advised me to plant oak trees round my fields to replace some old trees that will likely have to be cut down for safety. This was an experienced horse person… it is clearly not widely enough known that oaks pose a threat to horses.
ACORN TOXICITY: Last week was a devastating one. Three gorgeous welsh mares that I had scanned in-foal a month or two earlier lost their lives following acorn ingestion. This post is intended to raise awareness of the risks as the condition is not well understood. These horses had been on the same field for 5 weeks, there was no obvious change in weather conditions but overnight, two mares succumbed and were found dead in the field in the morning. One mare was quiet in herself. I attended immediately and found her to be rapidly deteriorating. Eve (excellent final year vet student) administered activated charcoal via a stomach tube while I arranged her immediate referral to Endells for intensive care in hospital. In spite of aggressive and prompt treatment, and an encouraging initial response, this mare tragically had to be euthanised that night. The mares had diarrhoea, with haemorrhage evident on re**al, and acorn husks were present in the droppings. Acorn toxicity is diagnosed by exclusion of other causes of death as there is no way to specifically diagnose it. A post mortem examination did not find any other cause of death. Our thoughts are with the owners and grooms who cared for these horses. And we encourage taking any actions possible to limit ingestion of acorns, even if historically there have been no problems in the horses/on the land as this desperately sad case serves to remind us that it is unpredictable, and not a fully understood condition, but that the risk is real, and death occurs very rapidly after ingestion with treatment typically being unsuccessful.