Horses won’t usually choose to eat acorns if they have enough forage at their disposal. However, there is evidence to suggest that some horses will develop a taste for acorns once they have tried a few and may actively seek them out. Ingesting a small number of acorns will not cause a horse any issues but large amounts of acorns are a different story.
It is fairly easy for a hungry horse to eat several kilos of acorns in a relatively short period of time and these can lead to a fatal overdose. Some horses appear to be more susceptible to acorn poisoning than others. This could mean that they have a lower tolerance of the toxins in acorns.
Indeed, the acorns, leaves and branches of the oak tree can all be problematic. It is important to be vigilante about acorns. The tannin found in them are poisonous to horses and can lead to gastroenteritis, bleeding in the gut and kidney failure. Horses are at increased risk in years when the trees produce an unusually high abundance of fruit.
Acorn poisoning is most often fatal and there is no treatment available. Vets can offer only charcoal feeds, Epsom salts and liquid paraffin which move things through the gut. Horses can be supported with fluids and electrolytes.
What can you do?
It helps if you can fence off oak trees to keep horses away from fallen acorns. Pick up any acorns that you can. Check pastures regularly and especially after high winds and storms which will cause more acorns to fall. If necessary, move horses to another field during the autumn when the acorns are falling.
If your horse has been known to consume acorns, then it is important to monitor them for signs of poisoning.
The earliest sign of acorn poisoning is a quiet horse. Further symptoms include colic, depression, loss of appetite, constipation and later, bloody diarrhoea. Weight loss, a smell of ammonia on the breath, excessive urination, increased thirst and jaundice may also be observed. If you suspect acorn poisoning, then it is vital that you call your vet immediately. Do not delay your horse’s treatment by monitoring them for a period of time before seeking help as it could then be too late to do anything for them.
There have been reports of malformed foals and abortions in mares who have consumed significant quantities of acorns during the second trimester of pregnancy.
The prognosis for a poisoned horse varies. If the kidneys or gut have been damaged, it isn’t always possible to save the horse.