Common Causes of Founder/Laminitis in Horses

Spring will soon be in the air! Grass will be growing, flowers blooming and everything will be coming alive. We will get to enjoy longer days and more sunshine! What could be wrong with that right?

Well if you have a horse prone to grass founder, this may present a serious problem. Laminitis or Founder, as it is commonly called, is inflammation of the laminae of the horse’s foot. The 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). The sensitive laminae interlock with insensitive laminae lining the hoof, much like interlocking fingers to keep the coffin bone in place within the hoof.  Horses suffering from Laminitis or Founder experience 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 end in the horse having to be euthanized.

Laminitis is triggered by a repeated concussion on hard ground (road founder), grain overload, retained placenta, hormonal imbalance (Cushing’s syndrome), certain drugs (corticosteroids), obesity and lush grass.

In the case of grain or grass founder, the longer days and more sunlight brings increased photosynthesis in grasses and plants which results in starch, sugar and fructan production. This accompanied with the cooler temperatures at night prevent the plants from using these sugars and they start to accumulate. The horse's small intestine doesn't digest fructans very well so it passes through the small intestines to the large intestines. When they reach the large intestine the organisms there ferment the new substrates rapidly which causes the production of lactic acid, bacteria and compounds called vasoactive amines as well as a drop in PH.  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. 

Later in the year, when the day and night time temperatures are more consistent, most of the fructan produced by the plant during the day is used up each night. This new information not only helps us understand that cause of grass founder but also provides us with a number of strategies to reduce the intake of fructans by grazing horses. 

Read more about Laminitis (Preventing spring time laminitis/founder)