Seedheads Can Cause Mouth Ulcers


foxtail seedheads by Neil Rhodes, UTIA

Foxtail seed heads contain stiff yellow-to-brown bristles which can cause physical trauma to a horse’s mouth when the horse eats hay containing the seedheads. The horse can get mouth blisters, along with gastrointestinal and skin irritation. Photo by N. Rhodes, courtesy UTIA.  

Horse owners should check hay for the presence of foxtails before feeding it to their animals. Mouth ulcers, also called hay blisters, can be caused when horses ingest foxtail (Setaria species). Foxtail seedheads are green to light green in color, and resemble a bottle brush or a  fox tail.

Jennie Ivey, University of Tennessee Extension Equine Specialist, says foxtail does not produce a chemical toxin dangerous to horses, but rather the structure of the plant itself can cause physical harm. “Microscopic barbs on the seed heads of stems of foxtail can cause physical trauma to the mouth leading to mouth blisters, irritation to the gastrointestinal tract, and occasionally the horse’s skin,” Ivey states. The leaves do not cause trauma and can be consumed, but are not recommended forage sources for horses.

Inspection of hay and pastures for seedhead presence is a simple method for prevention. “If moderate amounts of foxtail are found in hay, do not feed the bale and remove the remaining hay to prevent consumption,” says Ivey, “Additionally, monitoring horses’ gums and lips for any sores can help detect presence of these species,” she adds. If ingested for long periods of time, weight loss may occur in addition to mouth ulcers.

Foxtail can be difficult to control. “Timely mowing of pastures will help minimize or reduce seed production,” Ivey mentions, “but prevention of seedhead development is the best way to protect your horses.” Currently there is no herbicide available to remove foxtail or from hayfields or grass pastures; therefore, management to suppress seedhead presence is of great importance. If you suspect your horse is having complications from ingesting foxtail, contact your veterinarian.

For help in managing your hayfields, grass pastures and other forage or equine questions, contact your county extension office or visit the new UT Extension website for equine issues and events:​

Through its mission of research, teaching and extension, the University of Tennessee Institute of Agriculture (UTIA) touches lives and provides Real. Life. Solutions.



Dr. Jennie Ivey, 865-974-3157,