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Laminitis (1)

By Carla Huston
Spring brings warm weather, longer days and more riding time, but it also brings a danger to horses that can incapacitate one for life. Episodes of laminitis are common this time of year as horses consume the new grass in their pastures; but while the effects can be long-lasting and devastating, prevention is possible. And if your animal does develop laminitis understanding its course will help you reduce the damaging effects and manage the afflicted horse for maximum comfort and usefulness.
The white line of the foot marks the division of the sensitive and insensitive laminae, and laminitis occurs when these laminae become inflamed. The normal blood flow to these tissues is disturbed, especially in the toe area; this causes an interruption in the supply of oxygen and nutrients to the laminae, without which the cells die. Inflammation results, along with pain and swelling. Once this has occurred, separation of the sensitive and insensitive laminae follows and is permanent. A veterinarian or farrier can identify this situation by paring the sole at the toe and seeing the telltale elongation of the white line.
This acute phase of laminitis is extremely painful for the horse and may be attributed to many sources. Carbohydrate overload, systemic infection, retained placenta and extreme weightbearing on one limb are just a few causes. This time of year excessive consumption of lush green grass is a leading instigator of laminitis. Horses that are overweight, especially those that have developed a crest in their neck (indicating an excessive amount of fatty tissue), are particularly prone to laminitis. Ponies, too, show a high incidence, perhaps because of their metabolism.
Signs of acute laminitis are profound and are mostly linked to the animal's response to the pain. Usually only the forefeet are affected, and the horse takes on a characteristic stance with the hindlegs well under the body and the front extended forward. This position allows the animal to take pressure off the front feet. The horse is very reluctant to move, and when he does he has a stiff-legged gait, setting the heels down first. If all four feet are involved the animal will spend a great deal of time lying down. Examination of the foot itself will reveal an elevated temperature in the hoof at the wall, sole and coronary band. A pounding pulse is present in the digital arteries, most readily felt at the fetlock joint.
Founder occurs after the horse has passed through acute laminitis; it may happen in the initial episode or during a later attack. The identifying factor of founder is rotation of the coffin bone within the hoof capsule. Often accompanying it is a dropped sole. Because the laminae are damaged, the internal structures lose their support, and the pull of the deep digital flexor tendon causes rotation. If the rotation becomes advanced the coffin bone can eventually penetrate the sole of the foot. The degree of rotation can only be determined by radiographs. Hoof growth is altered also at this point. The development of new wall is impaired, especially in the toe region. Rings on the hoof wall illustrate the changed growth pattern and are very prominent in chronic founder, often diverging from toe to heel.
Treatment of acute laminitis consists mainly of eliminating the cause and alleviating the pain. In the case where overconsumption of grass is the culprit, the animal needs to be moved to a drylot and kept on a diet of hay and water. Historically, treatment included a regimen designed to decrease the temperature of the foot and diuretics to flush the horse's system of toxins, however, this is only successful when caught in the very early stages. Walking is important for blood flow within the foot, so the horse should not be confined to a stall. Too much exercise, though, is risky as it may promote more rotation of the coffin bone. Keep the animal on soft footing to reduce concussion on the sole and provide sufficient bedding so that he can lie down with comfort. The veterinarian may prescribe drug therapy to alleviate the intense pain in the early stages.
The farrier plays a crucial role in maintaining the horse with laminitis and especially founder. Proper trimming and therapeutic will often restore all but the most severe cases to a higher comfort level, while milder ones may be able to work again. The most effective shoeing regimen involves a bar shoe, straight, egg or heart, that transfers pressure from the injured toe area to the heels. Many horses, after application of the appropriate shoe, will walk off displaying little discomfort. These shoes require careful maintenance, though; they must be cleaned daily and checked for tightness against the foot, and the horse cannot be turned into muddy paddocks. The farrier should visit the horse every four to eight weeks to trim the hoof or reset the shoe, since it is essential that the heels and toes of the affected feet be kept balanced and in the proper proportions. For the owner management consists mostly of carefully monitoring the animal's diet and workload. It is also the owner's responsibility to involve both the veterinarian and farrier in the horse's rehabilitation schedule. These professionals are necessary for recovery. Applying and resetting shoes may require the veterinarian's presence and the use of a tranquilizer as the pounding of nails in the feet may prove painful. Periodic radiographs of the coffin bone are also helpful in tracking the progression of the condition and making shoeing decisions.
With the help of a professional farrier and veterinarian, and conscientious care from the owner, the horse with laminitis or founder has a promising future. He may not return to the previous level of work, but will certainly have a more comfortable life. Quick identification of laminitis and immediate treatment will help limit the effects. Proper management will slow or prevent its progression. But the best bet is to take all steps possible to diminish the chance of laminitis occurring.