Laminitis
Laminits means inflammation of the sensitive laminae which lie between the hoof and the bone of the foot (pedal bone). The basic problem is a lack of oxygen reaching the tissues, but this in turn is caused by a decreased blood supply to the structures of the foot. What happens is that various substances in the blood can cause constriction of small blood vessels, and the laminae are supplied by a network of narrow vessels that start as tiny arteries bringing blood into the foot, gradually becoming veins draining the blood from the foot. When the vessels constrict, the tissues start to die. If sufficient of the laminar tissue is destroyed, the pedal bone will no longer be attached to the inside of the hoof and will rotate within the hoof, so that its sharp point is now pressing down towards the sole.
Cause
The most common cause is a high sugar intake, eg from rich grass; this involves the stomach wall to release endotoxins that ultimately cause the blood vessel contraction. It can also be caused by any condition that leads to toxaemia or septicaemia, such as retention of foetal membranes after foaling, or even by excessive trauma to the feet such as a localised hoof abscess which has weakened the laminar attachement.
Symptoms
Laminitis starts as an apparent stiffness, with the horse unwilling to walk. It is generally distressed, trembling and sweating. In the less affected case the horse stands alternately lifting one foot after the other. Generally the front feet tend to be affected more severely than the back, and as a result the horse stands with the hind legs underneath the body and the front legs extended in an attempt to lessen weightbearing and, therefore, pain in the front feet. Because it takes more effort to push blood around the coronet and back up the leg rather than through the normal blood vessels in the feet, a bounding, fast pulse can be felt in the arteries underneath the fetlock. The horse may also lie down more and be unwilling to stand.
Treatment
Irreversible changes occur in the laminae within the first twelve hours, so it is essential to start treatment immediately.
-using either acetylpromazine or clenbuterol given by mouth will increase the blood supply to the laminae by dilating the blood vessels
-in all but the mildest of cases the fitting of a heart-bar shoe or rubber frog pads will support the pedal bone
-proper trimming of the feet is essential in all cases
-sand is the best bedding for laminitis cases
-pain killers are necessary
-complete box rest is essential
-full recovery may take many months. Moreover, just because the horse becomes sound, it does not mean that the laminae have recovered completely.
