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What is Showy Crotalaria Poisoning?

A member of the bean family, showy crotalaria is a summer weed with large bright yellow flowers that is most likely to be seen in mid to late summer. Along with some other species of crotalaria, this plant has the nickname “rattlebox” as when the plant’s pods dry, they make a rattling sound in the wind. All portions of the plant, whether alive or dried and in hay, are toxic to horses, with the seeds being the most toxic. Toxicity due to pyrrolizidine alkaloids can ultimately lead to liver failure in horses. Horses will usually avoid eating showy crotalaria unless there is nothing else for them to eat.

Showy crotalaria is a member of the bean family and is a summer weed that contains alkaloids that are toxic to horses, causing a variety of symptoms.

Symptoms of Showy Crotalaria Poisoning in Horses

Should your horse experience showy crotalaria toxicity, you may see the following symptoms:

  • Diarrhea
  • Minimal appetite
  • Weight loss
  • Yellow color in his gums and eyes
  • Fever
  • Mild colic
  • Photosensitization 
  • Change in behavior
  • Head pressing
  • Wandering aimlessly
  • Generalized weakness
  • Lack of coordination
  • Coma


Throughout the world there are over 600 species in the genus Crotalaria; these are known as rattlebox, rattlepod, shake shake and devil-bean. They are members of the pea/bean family, making them good soil builders as their roots support nitrogen-fixing bacteria, which will make the quality of soil better. Several of the species were brought to the United States, however it was found that the seeds were toxic to livestock; these plants are now considered noxious weeds.

Toxicity can occur when your horse grazes on the plant (typically something he avoids with the exception of during drought conditions), as well as if the plant is mixed with hay, silage or pellets.

Most common in showy crotalaria poisoning is when horses are fed contaminated hay and feed. It will take consuming only 1.5 to 3% of their weight of the plant to begin to show symptoms of toxicity. The poisoning can be acute, which occurs when a large amount of the plant is eaten and symptoms appear within a few days, or the more common chronic form where it will take months to years for symptoms to be seen.



Causes of Showy Crotalaria Poisoning in Horses

The cause of toxicity in the showy crotalaria is the pyrrolizidine alkaloid. The toxin will cause irreversible damage to the liver of your horse as it will get in the way of the liver cells ability to regenerate. Toxicity is cumulative; if your horse eats a large quantity of the plant at one time he will show symptoms of acute liver failure relatively quickly. More often, horses will eat small amounts of the plant over a longer period of time, which will gradually result in liver failure. 



Diagnosis of Showy Crotalaria Poisoning in Horses

Should you notice your horse consuming showy crotalaria, have a sample of it ready to show to your veterinarian, as that will help in diagnosing any concerning symptoms he is experiencing. If you did not see him ingest the plant, however suspect he consumed something that he shouldn’t, a sample of the plants he has had access to will also be helpful. 

Your veterinarian will conduct a full physical examination of your horse, as well as asking questions about the symptoms you have noticed, when you first noticed them, and any changes you that have occurred. Lab work will be conducted, to include a complete blood count (CBC) and chemistry panel in order to check his organs and blood levels. A urinalysis may also be administered in order to check the function of your horse’s kidneys. Depending on the symptoms your horse is experiencing as well as the results of the physical examination, your veterinarian may recommend other types of testing. 



Treatment of Showy Crotalaria Poisoning in Horses

While there is no antidote for showy crotalaria poisoning, your veterinarian will seek to provide supportive care. Fluid therapy, for example, can be administered to ensure that he remains hydrated. If he is not interested in eating, your veterinarian may consider feeding him by tube. It is likely your veterinarian will recommend keeping him in a stall for monitoring and for his comfort during his treatment. Other treatment options will depend on the symptoms that your horse displays. Some horses experience breathing difficulties, for example, for which oxygen can be provided. The prognosis for showy crotalaria poisoning is poor, particularly once the horse is showing symptoms. Even if he is not showing symptoms, he may have lesions on his liver. 



Recovery of Showy Crotalaria Poisoning in Horses

It is important to follow the recommendations of your veterinarian to ensure the best outcome for your horse. In addition, you will want to check the areas that your horse has access to in order to be sure that there are no additional showy crotalaria plants that he can try to eat. An expert in horticulture can be helpful in identifying potentially noxious plants on your property.



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Showy Crotalaria Poisoning Questions and Advice from Veterinary Professionals

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