Avocado Tree Poisoning in Horses

Avocado Tree Poisoning in Horses - Symptoms, Causes, Diagnosis, Treatment, Recovery, Management, Cost

Most common symptoms

Anemia / Lethargy / Poor Appetite / Swelling / Weakness / Wound


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Most common symptoms

Anemia / Lethargy / Poor Appetite / Swelling / Weakness / Wound

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Avocado Tree Poisoning in Horses - Symptoms, Causes, Diagnosis, Treatment, Recovery, Management, Cost

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What is Avocado Tree Poisoning?

If your horse eats the bark, leaves or the fruit of the avocado tree, the effect of the toxin causes respiratory distress and fluid around the heart, with the tongue, mouth and face suffering from swelling. The avocado tree contains a substance called persin, which is the toxin that can cause your horse to become seriously ill. It can affect your horse enough to cause their demise, so avoiding grazing your horse near an avocado tree is well advised.

The common name for the avocado tree is alligator pear and it is very toxic for your horse. All parts, from leaves to the fruit, carry the toxin.

Symptoms of Avocado Tree Poisoning in Horses

  • General weakness
  • In later stages the inability to get up again once they have lain down
  • Loss of appetite
  • Inability to eat because of the swelling around the mouth
  • Respiratory distress with laboured breathing such as shortness of breath
  • Fluid around the heart, and ventral abdomen
  • Swelling of the tongue and face 
  • Colic-type symptoms 
  • Neurologic dysfunction 
  • Irregular heartbeat


  • The avocado is the cause of the toxin that causes so much damage to your horse
  • The avocado comes in many varieties including Haas, Fuerte, Gwen and Ettinger
  • All varieties are poisonous to your horse as they contain the toxin persin
  • The leaves contain the highest levels of toxin, including dried leaves
  • Avocado trees shed their leaves continuously
  • They can be fatal to your horse

Causes of Avocado Tree Poisoning in Horses

  • An unidentified cardiac toxin causes myocardial necrosis which is death of heart muscle cells
  • This unidentified cardiac toxin affects the tissue around your horse’s heart
  • It is also a possible cause for the fluid that accumulates around the heart
  • The toxins cause inflammation of the mammary glands in lactating mares 
  • Grazing usually causes noticeable ill-effects within a short period of time 
  • Persin is the known highly effective toxin within the avocado 
  • The leaves, fruit, bark and the seed are all toxic to your horse 

Diagnosis of Avocado Tree Poisoning in Horses

If your horse has ingested leaves blown over the fence from a neighbouring avocado tree, or has been grazing near one, the signs will be very noticeable as the toxin goes to work. Some horse owners have awoken to find their horse with hugely swollen lips, face and tongue which causes respiratory problems, and all because they were unaware of the fact that the avocado is toxic to their horse. It is so serious that some people have lost their horses to this seemingly innocent plant. The veterinarians have no known antidote, but may help your horse to flush it out of its system. 

They will also be able to do a physical examination and may take tests to find the extent of the toxicity. Immediate removal from the paddock where the tree is growing is vital. Rest is important and it may take a few days before your horse can eat again, but once the appetite returns you should provide clean quality food and fresh clear water. Some horses have returned to good health whereas others have not been so lucky. It seems to depend on the amount of leaves, bark or the avocado pod that makes the difference.  Ongoing research is now being done on the effects of avocado on horses, and to raise the awareness and enable owners to exercise caution.


Treatment of Avocado Tree Poisoning in Horses

This unusual and often misunderstood toxic condition that may affect your horse is still in the early stage of providing any sort of vaccine or cure. Prevention is the best course of action. Any avocado tree that is growing in a paddock used for grazing needs to be assessed whether to keep the tree and mark the paddock as off limits for large animals like your horse or any cows. If you want to keep the paddock for grazing, the only alternative is to get rid of the tree. Even if you do not have any growing on your land, if the neighbour has an avocado orchard then you need to be very careful that the fruit and leaves don’t invade your property. 

If you suspect that your horse has suffered the effects of avocado, remove them from the source and keep him calm and quiet as you wait for the veterinary specialist. Your veterinarian may be able to reduce any further absorption of the toxin by drenching the stomach through a tube using copious fluids, liquid paraffin or activated charcoal. This may stop the absorption of the eaten avocado, and allow your horse to recover in a few days. Most horses return to normal in a short time, but those that have been grazing heavily (such as when food is scarce and that is the only option) the prognosis is grim with the heart and lungs showing irreparable damage.

Recovery of Avocado Tree Poisoning in Horses

Management of this condition requires a total avoidance of any contact between your horse and the avocado tree including the leaves, bark and fruit. The recovery rate depends a lot on the amount of leaves, bark or fruit your horse has eaten. If it was just a few mouthfuls your horse may just feel a bit sick, but if he has been in the contact for several days and eaten large amounts then recovery may be doubtful. Calling the veterinarian as soon as you detect a problem and you link it to the avocado may be the deciding factor in regards to recovery time. In most cases, if you remove your horse immediately, seek medical assistance and allow your horse time to recover the prognosis is reasonable. Always be vigilant because the avocado tree is very dangerous to equines.

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