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Showy Crotalaria and Horses

Published: November 5th, 2012

Category: Medicine, News

The dried pods of the Showy Crotalaria

Information provided by Dr. Sarah Reuss, Service Chief and Veterinarian of UF Large Animal Internal Medicine, Clinical Assistant Professor, DACVIM, VMD

What is Showy Crotalaria?

Showy crotalaria is a member of the bean family and is considered a weed in Florida. This and some other species of the crotalaria are nicknamed “rattlebox” because when the pods of the plant dry, they “rattle” with the wind. Showy crotalaria is a summer weed and would most likely be found in mid to late summer.

Is Showy Crotalaria (aka “Rattlebox”) poisonous to horses?

Showy crotalaria is toxic to horses. All portions of the plant (whether alive or dead and baled in hay) are toxic, with the seeds being the most toxic.

How does Showy Crotalaria affect horses?

The toxic principle of crotalaria is something called a pyrrolidizine alkaloid. This class of toxins causes irreversible damage to the liver because it interferes with the ability of the liver cells to regenerate. So toxicity is a cumulative effect. A horse who ate a large amount all at one time would quite quickly show signs of acute liver failure. But more commonly what we see are horses who have eaten very low levels of these plants over weeks to months to years and have gradually developed liver failure.

Fortunately most horses avoid eating crotalaria unless there is nothing else available to them. Palatability will also increase with frost or drought. Horse owners are encouraged to remove any known plants from their fields and keep an eye on new hay sources for any dried crotalaria baled into the hay.

What are the clinical signs of Showy Crotalaria toxicity?

  • Diarrhea
  • Poor appetite
  • Weight loss
  • Icterus (yellow color of the gums and eyes)
  • Fever
  • Mild colic
  • Photosensitization – “sunburn” of non-pigmented skin
  • Neurologic signs – behavior change, head pressing, coma

What do I do if I suspect my horse has eaten Showy Crotalaria?

Bloodwork may show signs of toxicity before the horse has shown any clinical signs. So if you are concerned that your horse may have been exposed, have your veterinarian check a blood chemistry or contact the UF Large Animal Hospital.