What is Yellow Locust Poisoning?

Yellow locust is a plant that can be found in many regions and is known by many names.  This plant produces toxins that cause protein synthesis and gastrointestinal irritation upon ingestion by your horse.  The symptoms these toxins cause in your horse can be caused by many other things as well.  In order to come to a proper diagnosis of the cause, your veterinarian will need to perform tests and possibly take radiographic images in order to determine the cause.  Treatment is supportive and supplemental as there is no antidote.  Death from yellow locust ingestion can occur but is rare; therefore prognosis of recovery is good.

Any type of paralysis, heart arrhythmia or respiratory distress is considered a medical emergency.  These are all possible symptoms of poisoning from the yellow locust plant and a veterinarian should be contacted immediately. 

Symptoms of Yellow Locust Poisoning in Horses

Many symptoms of yellow locust poisoning can be vague or can accompany many other types of illnesses.  Symptoms may include but are not limited to:

  • Depression 
  • Weakness
  • Loss of appetite
  • Nausea 
  • Diarrhea
  • Anorexia
  • Papillary dilation 
  • Mydriasis
  • Irregular pulse
  • Laminitis 
  • Posterior paralysis
  • Difficulty breathing
  • Death (uncommon)


The yellow locust can be found in many regions including fencerows, pinelands, dry woodlands, old fields, and roadsides but really thrives in clay soils.  To some people, this plant is considered an ornamental tree while other consider is a potential problem; the tree produces compound leaves and spines similar to those found on a rose.  There are many common names this plant is known by including pea flower locust, locust tree, black locust tree, false acacia, bastard acacia, and black acacia.  In the scientific and sometimes medical communities, this plant is known by its scientific name of Robina pseudoacacia and belongs to the Papilionaceae family.



Causes of Yellow Locust Poisoning in Horses

The toxin that the yellow locus produces is actually two:  two different toxo-albumins known as phytotoxin robinin and glycoside robitin.  While the purpose of the plant producing the toxin is unknown, we do know that the toxin can cause emetic and purgative effects on the one who ingests it.  The main effects of the toxin are protein synthesis and gastrointestinal irritation and the toxin can be found in the bark, seeds, and flowers of the plant.



Diagnosis of Yellow Locust Poisoning in Horses

Upon arrival, your veterinarian’s first step will be to ensure your horse’s condition is stabilized.  Once it is, she will proceed with her diagnosis.  She will begin by performing a full physical exam in order to make note of all of his symptoms.  In addition to this, she will want details from you about when the symptoms started and if they have been getting worse.  

In order to determine the extent of possible central nervous system (CNS) disturbances she will want to run a series of neurologic tests.  This will allow for evaluation of the specific symptoms, where they may be originating, and why.  There are many causes of CNS symptoms in your horse, with toxicity being one of them.

If your horse is experiencing breathing difficulties and the veterinarian cannot confirm the cause via auscultation, she may want to take radiographs.  This will allow her to check his lungs for air, fluid, masses, or other possible abnormalities.  She will need to rule out illnesses such as pneumonia in order to come to a proper diagnosis.

The veterinarian may recommend lab work so she can check his organ values and levels in his blood.  A complete blood count (CBC) and chemistry panel to check for generalized abnormalities is a good place to begin.  Depending on the results, she may want to run more detailed blood related tests.  As for other lab tests,  she will run a series of fecal tests to check for possible causes such as intestinal parasites or bacterial overgrowth if he is experiencing diarrhea.

There may be additional tests your veterinarian will want to run in order to rule out other possible causes of your horse’s ailment.  Of course, if your horse dies you can request a necropsy in order to determine the cause.  Necropsy findings from yellow locust poisoning can include lesions on and within the gastrointestinal tract.  This will give you a complete diagnosis to prevent your other horses from suffering the same poisoning.



Treatment of Yellow Locust Poisoning in Horses

During treatment and therapies, you will need to keep your horse stalled in order to closely monitor him.  There is no exact treatment plan of yellow locust poisoning as each individual case varies.  However, your veterinarian will treat your horse symptomatically as symptoms appear.  You will need to remove your horse from the source of the yellow locust plant immediately to prevent further ingestion.  The longer your horse ingests it, the more severe his symptoms will become.  

If he is suffering from breathing difficulties, she may want to supplement him with oxygen.  She may offer medications such as corticosteroids and antihistamines which will help reduce any inflammation and help him breathe easier.  She may also administer oral or injectable medications to relax his muscles, ease his breathing, and lessen his anxiety which may be contributing to the issue.  

If your horse has stopped eating or is eating only very small amounts, your veterinarian may try to tube feed him in order to keep his digestive system moving.  In horses, if the GI tract comes to a halt, it can lead to additional symptoms.  If your horse is experiencing other gastrointestinal related symptoms, for example diarrhea, she will start fluid therapy to ensure he stays hydrated and to flush the toxin out of his system.  Diarrhea is a major source of water loss in a horse so ensuring he stays hydrated is very important for his recovery.



Recovery of Yellow Locust Poisoning in Horses

While not impossible, death from yellow locust plant poisoning is uncommon.  To provide your horse with the best chance of recovery, you need to remove your horse from the plant source and prevent further ingestion.  If you do this and also provide him with appropriate veterinary supportive therapy his prognosis of recovery is good.  If your horse happens to be one of the rare few to die from yellow locust ingestion, a necropsy is highly suggested.  It will allow for a proper diagnosis of his cause of death and can help you prevent similar fates for your other horses.



Yellow Locust Poisoning Questions and Advice from Veterinary Professionals

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© 2022 Wag Labs, Inc. All rights reserved.