Laminitis and Founder in Horses
Laminitis is a serious hoof disease found in equines (e.g. horses, ponies, donkeys). Although it is very rare for laminitis to kill a horse directly, severe cases can result in the horse being put down for humane reasons (horse is in pain) or economic factors (horse is crippled and can no longer be used). Such euthanasia is sufficiently common that laminitis has become the second most common cause of premature horse death.
The term ‘laminitis’ comes from ‘laminae’, which is the tissue which connects the hoof bone (correctly known as the pedal bone) to the hoof wall. Damage to this tissue is known as ‘laminitis‘. In mild cases the tissue becomes inflamed and begins to break down, reducing the strength of the bone-wall connection. In more severe cases the connection is reduced to the point that the bone begins to move, rotating within the hoof and sinking down. In extreme cases, the hoof will actually go through the sole of the hoof. As the bone moves, it can cause further damage to blood vessels and other surrounding tissues. Longer term, this damage affects the hoof repair and growth mechanisms, resulting in various types and degree of abnormal growth (e.g. convex or flat sole, hoof wall rings, separation of sole and hoof wall). In mild cases, the horse can return to normal activities. In more severe cases, the horse will need to be retired or put down.
The term ‘founder’ is related to ‘laminitis’, but is used in different ways by different people. Some people use the term founder interchangeably with laminitis, others to describe the more advanced forms of laminitis (e.g. substantial hoof bone movement or the bone penetrating the sole).
There are various causes of laminitis but they can be grouped into three categories. The first is overly rich feed, which upsets digestion, resulting in the release of toxins into the blood, where they then travel to the laminae and cause inflammation and tissue break down. The second category is mechanical separation, where the laminae is damaged from repeated shocks to the hooves (from running or jumping or hard ground). The third category is toxins, either ingested in the feed, or produced internally as a result of an infection
Excessively rich feed results in changes to the bacteria population in the digestive system, causing the release of toxins by the bacteria. It occurs when a horse has too much carbohydrates or nitrogen, either from excessive amounts of rich feed (e.g. grain) or lush pasture. Pasture is most likely to be excessively rich in spring, when rain follows a drought, or if it has been fertilized. As some breeds (in particular, ponies) are more sensitive than others, one should take special care with sensitive breeds to restrict the amount of rich food and to keep them off rich pasture. Alternatively, one can put them on pasture for a limited time but use a grazing muzzle to restrict the amount they eat.
Mechanically caused laminitis most often occurs in competition horses, such as jumping horses or race horses, which are worked on hard ground. However, it can also occur to pleasure horses, if they are worked or travel on hard surfaces. One should try to avoid use of a horse on hard surfaces and when it is necessary to travel on hard surfaces try to reduce the pace as a walking horse will have less shock to its feet than a running horse. Ensure that the feet are correctly trimmed; in particular avoid over-trimming or trimming for long toes as these reduce the shock resistance of the feet. If the horse has shoes, ensure that the shoeing is done by a competent professional. Shock absorbing shoes (e.g. horse shoes with a rubber component) and boots are increasingly used, even in competitive sports, to reduce not only the risk of laminitis but also other shock related injuries.
Ensure that your horse goes not get external toxins from food which has mold, fungus or chemicals. Do not let them eat grass which has been chemically treated (e.g. with herbicides). Any serious infections should be promptly and aggressively treated, to prevent the infection from releasing toxins into the blood.
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