Laminitis / Founder

THE LAMINAE

The laminae make up the structure responsible for anchoring the coffin bone to the hoof wall. The laminae consist of an arrangement of non-sensitive laminae made of keratin and sensitive laminae that contain blood vessels and nerves. Both types are connected together in a dovetail fashion that suspend the coffin bone within the hoof. When the laminae become inflamed, the disease is termed laminitis. Causes of the disease are varied and quite unrelated. They can be grouped into metabolic, biomechanic and traumatic effects.

Laminitis is accompanied by interference of oxygen and nutrient supply to the feet that results in necrosis and detachment between the sensitive and non-sensitive laminae. The laminar region of the hoof at the toes is more predisposed to damage due to the anterior- posterior direction of the forces that are placed on the foot. The forelegs are most commonly affected because they bear more weight. When the connection between the sensitive laminae and nonsensitive laminae weakens, the coffin bone can rotate or sink. The forces that act to alter the coffin bone position during laminitis were classified by Coffman (1970) into tearing forces, driving forces and pulling forces.

 Causes of laminitis in the horse

Grain over-load , Retained placenta, Steroid therapy, Grazing on lush spring grass, Excessive weight bearing on one limb following injury to the opposite limb. Hard work on hard ground, Excess intake of cold water after hard exercise, Colic, Generalized disease, Overfeeding, Toxins

 The precise way that the destruction of the laminae starts is still unknown. There are variations among horses in their sensitivity to the disease. Factors such as obesity, nutrition, hoof conformation (laminar surface area), horn quality and type of work play critical roles.

The biomechanical forces that can alter the position of the coffin bone following an insult to the laminae (modified from Coffman 1970): Tearing forces (A) = Ground pressure on the toe. Driving forces (B) = weight of the animal. Pulling forces (C) = The pull of the deep digital flexor tendon on the coffin bone.

CLINICAL SIGNS & EMERGENCY TREATMENT

Laminitis can be divided into two main types: acute and chronic laminitis. The early acute laminitis is accompanied by lameness before the appearance of external changes in hoof conformation. Initially at the laminitic stage, the horse walks with short steps as if it were walking on stones after being trimmed too short. The farrier should be able to examine the feet for pain, increased surface temperature and digital pulse. Hoof testers suitable for horses are applied over the sole area at the margin of the coffin bone, taking into consideration that the horse may have been trimmed recently and therefore has sore feet.

Temperature of the hoof is examined by placing the palm of the hand over the toe and comparing between hooves for increased warmth. Digital pulse is checked by pressing with the fingers against the digital arteries situated below the fetlock and slowly releasing the pressure. Detection of pulse and/or increased temperature indicates an inflammation inside the foot.

The horse may place more weight on the heels when walking, in this way trying to remove weight from the painful toes. When the forelegs are affected, the horse places the hind legs well forward under the belly in a typical stance.

At the acute stage of laminitis your farrier can advise the owner to remove the cause if obvious (e.g., the horse was eating too much grain), and get medical help. Emergency aid for horses that are suspected of developing laminitis consists of pulling the horseshoes, trimming excess horn and placing the horse on soft sand or mud. Nail pullers are used to pull the nails one by one in order to minimize strain on the damaged laminae that can be caused by the pulloff's leverage. The toes are dubbed to decrease the lever arm effect on the toe (Linford 1990).

By providing the first aid, we reduce the forces that tend to rotate P3 but despite that, the disease can progress; therefore, laminitis should be treated as an emergency. The damage to the hoof tissue can be severe enough to cause rotation and protrusion of the coffin bone through the sole. Permanent or chronic laminitis could result in severe or unattended cases.

SHOEING THE CHRONIC LAMINITIS CASE

Chronic laminitis is accompanied by changes in hoof conformation. The pressure from the ground on the toes and laminar weakening causes abnormal widening at the white line and a convex toe. The flat sole caused by the pressure from P3 is uncomfortable to the animal when it walks on stones. Even with these changes, the hooves can be stabilized enough to carry the horse's weight as new laminar growth and keratin formation develop. Factors such as laminar surface area and strength, type of work performed and treatment play a role in the future use of the horse.

Treatment of chronic laminitis consists of regular trimmings to establish normal hoof conformation and realignment of the digital bones. It includes lowering the heels to align the coffin bone in a straight line with the other two phalangeal bones, and rasping the toe to reconstruct the foot axis. Shoeing of the chronic case includes removal of pressure from the sole and its protection with wide-web shoes that give the animal confidence when walking. The shoe can be made from 1" bar stock or a used rasp. Extended heels can provide caudal support that will remove stress from the toes and maintain an improved anterior-posterior balance following the lowering of the heels. In order to relieve pressure at the toe area, a section from the hoof wall is cut, leaving an open space between the hoof and horseshoe. To ease breakover, the hoof surface of the shoe is made concave and a rolled toe is added. Other types of horseshoes that can be used include a shoe with a leather pad packed with pine tar and oakum and the reversed shoe or egg bar shoe. Acrylics can be used to reconstruct the hoof wall when there is no evidence of inflammatory secretions from the hoof. The distance between the hoof and hoof surface of the shoe has to be observed regularly for signs of re-rotation of the coffin bone. If this occurs, the horse should be treated as for acute laminitis.

In conclusion, there is more than one method that your farrier can apply for the treatment of laminitis in the horse. Farrier/veterinarian collaboration is essential for increasing the horse's chance for recovery.