Laminitis: Definitions, Prevention, and Treatment
by Courtney Shumpert, DVM ----     Source: American Association of Equine Practitioners



The equine foot contains thousands of tiny lamina, structures within the foot that attach the coffin bone to the hoof wall. There are two types of lamina, sensitive (contains lots of nerve endings) and insensitive (contains no nerve endings). Laminitis, which literally means "inflammation of the lamina," results from the disruption of blood flow to the laminae. This inflammation permanently weakens the laminae and interferes with the bond between the hoof wall and the coffin bone. In severe cases, the bone can actually become separated from the hoof wall. When this happens, the coffin bone is allowed to rotate within the foot, become displaced (sink) and may eventually penetrate the sole of the foot. Laminitis can affect one or all four feet. It is most often seen in the front feet.
 
The terms "laminitis" and "founder" are often used interchangeably. However, there is an important difference in the two. The word founder literally means "to sink." Therefore, founder refers to a chronic or long-term condition which is associated with ROTATION of the coffin bone. (In mild or acute cases of laminitis, the coffin bone may not rotate or sink at all.)
 
The term acute laminitis refers to the clinical signs (symptoms) associated with the sudden or initial attack, which include pain and inflammation of the sensitive laminae.

   
Fig. a
 		Fig. b
 		Fig. c
Figure.a. (left) The normal relationship between the coffin bone and the hoof capsule. The parallel lines represent the laminae that anchor the coffin bone to the hoof wall. b. (middle) Rotation of the coffin bone following laminar damage. c. (right) Sinking or displacement of the coffin bone.

   

Although laminitis is a disorder of the feet, it is often caused by a disturbance somewhere else in the horse's body. The causes of laminitis are numerous and variable. The following is a listing of the common causes.

  • Dietary causes (grain overload, abrupt changes in the diet)

  • Sudden access to excessive amounts of lush green grass ("grass founder")

  • High fever or illness; toxins carried to the feet by the blood from elsewhere in the body

  • Severe colic

  • Retained placenta in the mare after foaling

  • Consumption of cold water by an overheated horse

  • Excessive riding or exercise on hard surfaces ("road founder")

  • Excessive weight bearing on any one leg (Example: a horse with an injury to the right front foot will bear more weight on the uninjured left front foot)

  • Various diseases of the hoof itself

  • Consumption of black walnut shavings (bedding)

SIGNS -

ACUTE LAMINITIS:

  • Lameness

  • Heat in the feet

  • Increased digital pulse in the feet (can be felt on the back of the ankle or pastern)

  • Pain in the toe region (when pressure is applied via hoof testers)

  • Hesitant gait (tiptoeing) or reluctant movement

  • Standing with the front legs extended in an attempt to bear more weight on the hind legs in order to alleviate pressure on the toes

CHRONIC LAMINITIS:

  • Rings in the hoof wall

  • Bruised soles

  • Widened white line ("seedy toe") This condition is often associated with blood pockets (seromas) and/or abscesses.

  • Dropped soles (flat feet)

  • Thick, "cresty" neck

  • Dished hooves (result from unequal rates of hoof growth)

TREATMENT:
Treatment may include the following, but will vary based on the needs of each individual horse. The SOONER a horse with laminitis receives treatment, the better!

  • Diagnosis of and treatment of the primary problem (if laminitis is the result of a disorder somewhere else in the body

  • Dietary restrictions (less and more bland feed)

  • Treatment with mineral oil via stomach tube to purge the digestive tract (this is done in cases of overeating)

  • Intravenous fluid therapy if the horse is ill or dehydrated

  • Drugs such as antibiotics to fight infection, anticoagulants to lower blood pressure, etc. (these will vary based on the needs of the individual horse)

  • Stabling the horse in deep shavings or on soft ground

  • Finding, opening, and draining any abscesses that may have formed

  • Corrective/therapeutic horseshoeing

  • X-rays are essential to determine if and how far the coffin bone has rotated (these can be used to determine the amount of damage and aid the farrier with corrective shoeing

Laminitis is a very serious condition which should be addressed immediately by a veterinarian. In many cases, prompt medical attention can significantly lessen the amount of damage done to the hoof wall. This is very important when you consider the fact that many horses recover completely and go on to lead long, healthy lives. However, in severe cases, euthanasia may be necessary for humane reasons. Your veterinarian can determine which course of treatment is best for your horse.

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