Toxic Weed of the Week: Crotalaria

Its been a rainy, wet summer which means that grass, weeds, and everything green is growing. While most weeds are harmless, there are a handful of toxic weeds that should not be allowed to grow in pastures grazed by livestock. One of the more common toxic weeds I see growing in pastures is Crotalaria (aka rattlebox).

In the south, Crotalaria grows in the summer and fall. It produces yellow flowers and has seed pods that are short and thick. All parts of the plant are toxic to horses and when consumed, Crotalaria causes irreversible damage to the liver. Over time, cumulative damage to the liver results in liver failure.

Early signs of Crotalaria toxicity are weight loss, diarrhea, poor appetite, and colic. As the toxicity progresses, the patient will become jaundiced and show symptoms of neurologic disease. This includes loss of balance, head pressing, abnormal mentation, and behavior change. Some horses also develop photosensitivity which leads to sunburn of non pigmented skin.

Unfortunately, there is no treatment for Crotalaria toxicity. If you suspect that your horse may have grazed on Crotalaria, bloodwork can help determine if there is liver damage. The best prevention, however, is removal of the weed from livestock pastures. Your local county UF IFAS Extension Office can help give recommendations on how to remove the weed safely from pastures and prevent re-growth.