Are Acorns Bad for Horses? Everything About Acorn Poisoning

Horses eat a lot of things but what about acorns? Wasn’t it common knowledge that acorns are bad for horses? Well, they are. Not only horses but cats and dogs too. That’s because acorns contain tannic acid, a substance that may cause kidney and liver damage if consumed in large enough quantities.

Usually, horses don’t eat acorns if they don’t have a choice. Call it an instinct but they know acorns aren’t good for them.

However, if they don’t have anything else to eat, hunger prevails. They’ll chomp down on acorns without a second thought. What happens next is easy to guess. Or is it? Keep reading to find out!

Are Acorns Toxic to Horses?

In short, yes. Acorn toxicity does appear, though it’s not very common. Horses would need to eat a lot of acorns to get poisoned. Acorns contain gallotannins, a natural acid that gets broken down into toxic molecules in the horse’s body. These toxins may damage the intestinal lining, stomach, blood vessels, and kidneys of the horse.

But, as I said, poisoning occurs only if the horse eats a large number of acorns. So, only if it’s feeling really hungry and doesn’t have food for days will it start eating acorns indiscriminately.

It could also be that the horse doesn’t find the forage very tasty or the pasture is poor. And then there are the horses that actively seek out acorns, developing some kind of addiction to them.

Horses can indeed eat so many acorns that they cause extensive damage to their stomach and kidneys. That’s when you have to step in and make sure they stop eating the acorns. And call a veterinarian because the situation may already be grave enough.

Will a Horse Die from Eating Acorns?

Death from acorns, while uncommon and unlikely, is technically possible if enough acorns are ingested by the horse. Liver and kidney damage can be so severe that the horse starts hemorrhaging internally.

Acute colic is another dangerous symptom that may become severe enough to cause death. Generally, the more acute the symptoms, the likelier it is for the horse to die.

How Many Acorns do Kill a Horse?

Scientifically, we don’t know this. We can safely assume that eating a few acorns is harmless to horses, though. However, to prevent any unsavory situation, make sure your horses never eat acorns or oak branches. That way, you can be confident that they won’t be poisoned and fall ill.

In North America, there are over 60 different oak species and plenty of horses everywhere. Still, cases of acorn poisoning are extremely rare, even in this situation.

The only way acorn poisoning becomes a thing is if the horse literally has nothing else to eat but oak branches and acorns. And this is the caretaker’s fault. You should always ensure that your horse has plenty to eat.

What to Do If Your Horse Eats Acorns?

If your horses develop an appetite for acorns, isolate them from the object of temptation. If there’s an oak tree in their paddock, build a fence around it so that horses can’t reach any branches.

Check the paddock daily and remove any branches or acorns knocked over by strong windstorms. Though, your best bet is to remove the oak tree entirely if you want to eliminate the risk.

One other thing you can do is check whether your horse has food available in its paddock, other than the acorns. Do you provide it with enough hay and grass to graze on?

If there are too many horses and too little food, famine will become a problem. And then the horses start eating oak branches, leaves, and acorns. You can manage the situation quite easily, though – offer more food!

Symptoms of Acorn Poisoning in Horses

Acute acorn poisoning manifests in a wide variety of symptoms, most of which aren’t pretty to behold.

Bowel obstructions and ruptures are not uncommon if the poisoning is grave enough. Kidney and liver damage are another potential effect of acorn overconsumption.

Colic, diarrhea, gastric upsetting, digestive tract issues, all these are possible symptoms of acorn poisoning.

When the symptoms become more acute, even death is a likely outcome, especially if the horses keep consuming acorns. But you’d have to be really unobservant to notice these symptoms.

Other signs of acorn poisoning include:

  • Depression
  • Constipation
  • Mouth ulcers
  • Dehydration
  • Lethargy
  • Colic
  • Increased lying down
  • Reduced appetite
  • Acorn husks in droppings
  • Poor hair coat
  • Abdominal pains
  • The scent of ammonia in the horse’s breath
  • Pain while defecating
  • Frequent urination and blood in the urine

Acorn poisoning will manifest in a gradual onset of the symptoms the horse keeps on consuming oak parts or acorns. Unless you stop this behavior, the horse’s health state will become worse in a short time.

However, no one knows what the toxic dose of acorns is, not even scientists. That’s why I recommend zero consumption of acorns for horses, in general.

Can a Horse Recover from Acorn Poisoning?

Only a veterinarian can tell you that. It largely depends on the degree of acorn poisoning and how severe the symptoms are. But, in general, acorn poisoning isn’t deadly for horses because they never get to consume that many acorns.

Your veterinarian may recommend intravenous fluidization because dehydration is a primary symptom of acorn poisoning in horses.

Activated charcoal is a great treatment used for acorn poisoning, but it’s only good immediately after the horse consumed acorns. Mineral oil and calcium hydroxide, sodium sulfate, magnesium sulfate, are all good if provided early in the illness phase.

If you want to prevent acorn poisoning, feed your horse supplements that contain 10-15% calcium hydroxide.

It’s not too difficult to save your horse from acorn poisoning, as long as the symptoms aren’t too severe. Make sure the horse stays hydrated at all times and talk to your veterinarian at all times. They’ll know what to do.


To sum things up, acorns are toxic to horses but only in large quantities. I can’t tell you what a large quantity of acorns is because I don’t know. We can only estimate and guess.

But to be safe, don’t let your horse eat any acorns or oak leaves and branches. If they do, immediately contact your veterinarian and take the necessary measures outlined by the vet. Acorn poisoning can be deadly but these are rare cases!

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avatar Noah
I’m Noah, chief editor at VIVO Pets and the proud owner of a playful, energetic husky (Max). I’ve been a volunteer at Rex Animal Rescue for over 2 years. I love learning and writing about different animals that can be kept as pets. read more...

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