Laminitis is often called founder, but the two are really not the same thing. Laminitis is the actual damage to the tissue of the laminae of the hoof, while founder is the ongoing conditions that occur that are a result of the laminitis. Since most horse owners interchange the two terms, it is always important to confirm which condition they are referring too. Laminitis as well as founder can occur in a range of severities from mild to severe and debilitating to the horse. In very severe cases of laminitis and the resulting founder the horse may have to be destroyed if they are no longer able to bear weight on the foot or feet.
Laminitis can be caused by several factors including diet and stress. In many horses laminitis is a direct result of overweight horses being turned out on lush pastures and overeating, or getting into feed bins and eating grains or feed pellets without restriction. Some horses may also show signs of laminitis by eating large amounts of grass clippings from lawn grasses. Some toxins, bedding containing black walnut shavings and drinking large amounts of cold water when the horse is overheated are also known to cause laminitis. Stress of trailering or even competitions may also very occasionally cause laminitis in some high-strung horses. Founder or laminitis may be acute or chronic, but each attack will further damage the laminae of the foot, resulting in greater overall damage. The laminae of the hoof is the area responsible for supporting the coffin bone and distributing the horse's weight out to the strong hoof walls. When laminitis is present, the laminae breaks down, resulting in the weight being directly on the coffin bone, resulting in pain to the horse and a rotation of the coffin bone. In severe cases this damage is permanent and very debilitating.
A horse with laminitis or founder is relatively easy to diagnose because of the characteristic behavior it will exhibit. Since there is a great deal of pain in the feet, usually the front feet, the horse will stand with his or her back legs pulled up under the body and the front legs stretched forward. The horse will not want to walk and will be very stiff and choppy in movements, especially on the front legs. If all four feet are involved the horse will often lie down and refuse to stand. They will usually not eat or drink and will appear very listless and uninterested in their surroundings. The hoofs and lower legs will feel feverish and hot to the touch.
Treatment at the first signs of laminitis or founder is essential. Walking the horse in very soft ground will help with decreasing swelling and increasing circulation. Never walk the horse on hard ground as this can further damage the coffin bone. If the horse is refusing to walk, don't force the issue. Provide aspirin as per your vet's recommended dosage until the vet can get there. Usually the vet will start treatment with bute (more properly known as phenylbutazone), either by IV or orally, depending on the severity of the condition.
Proper management of feed as well as corrective shoeing to minimize the pressure on the sole of the foot is essential in most cases where an acute or chronic problem with laminitis has occurred, especially if it is progressed through to founder.