04/02/2026
DO YOU KNOW WHAT CAUSES GRASS FOUNDER?
Spring is a wonderful time of the year, but it may be the beginning of some serious problems for horses vulnerable to grass founder — like horses that are over the age of 10, easy keepers, overweight or cresty-necked.
Laminitis or founder, as it is commonly called, is inflammation of the laminae of the horse’s foot. Laminae are the delicate, accordion-like tissues that attach the inner surface of the hoof wall to the coffin bone (the bone in the foot). A horse suffering from laminitis experiences a decrease in blood flow to the laminae, which in turn begin to die and separate. The final result is hoof wall separation, rotation of the coffin bone and extreme pain. In severe cases, the coffin bone will actually rotate through the sole of the horse’s hoof where it becomes infected and can ultimately lead to the horse having to be euthanized.
Laminitis can be triggered by different causes, like repeated concussion on hard ground (road founder), grain overload, retained placenta, hormonal imbalance (Cushing’s syndrome), obesity, and lush grass.
In cases of grass founder, the sugar fructans produced by rapidly growing grass stimulates an overgrowth of bacteria in the horse’s large intestine. The bacteria produce and release toxins (endotoxins) that are carried by the bloodstream to the foot where they cause damage to the laminae and small blood vessels.
The best way to deal with laminitis is preventing and managing the causes under your control. Consult your equine practitioner for further information and to formulate a plan tailored to your horse's individual situation. If you suspect laminitis, consider it a medical emergency and notify your veterinarian immediately.
