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By James K. Belknap, DVM, PhD, DACVS, Department of Veterinary Clinical Sciences, College of Veterinary Medicine, Ohio State University
Among the many disorders that can affect the foot of a horse are laminitis, navicular disease, puncture wounds, infections, keratoma, pedal osteitis, pyramidal disease, quittor, sandcrack, scratches, seedy toe, sheered heels, sidebone, thrush, bone cysts, bruises, corns, cankers, and fractures.
Laminitis (Founder)
A horse’s foot has 2 types of laminae (tissue layers). The sensitive laminae are attached to the pedal bone. The insensitive laminae are the layers of tissue just inside the hard exterior of the hoof. The word laminitis means “inflammation of the laminae,” and it can refer to either a short-term (acute) inflammation or the disease caused by longterm or repeated (chronic) attacks of inflammation. Laminitis can develop in the forefeet, in all 4 feet, or in the hindfeet only. Supporting limb laminitis can be seen in a single foot, usually as a complication of a severe lameness or bone injury in the limb on the opposite side of the body.
Acute laminitis occurs when cells on the insensitive laminae fail to attach to the sensitive laminae. Because the laminae suspend the pedal bone within the hoof, failure of laminar attachments results in catastrophic displacement of the pedal bone. The heavy weight of the horse and the pull of the flexor tendons can contribute to the displacement. The pedal bone can rotate, sink, or tilt within the hoof. If rotation progresses, a hole may form through the sole of the foot.
Three disease states are thought to be associated with laminitis: 1) diseases that cause bacteria or bacterial toxins to spread through the blood (called sepsis and endotoxemia, respectively), 2) hormonal disorders (such as equine metabolic syndrome), and 3) pain or inability to use the limb on the other side of the body. The most common causes of laminitis are ingestion of too much grain, grazing of lush pastures (especially in ponies or overweight horses), and excessive exercise or repetitive trauma. Other causes include generalized infections, ingestion of black walnut heartwood shavings, retained placenta after delivery of a foal, colitis, colic, and treatment with corticosteroids and certain other medications. The risk is higher in ponies and in horses that are overweight and unfit. The number of cases of acute laminitis tends to increase whenever there is a flush of new grass.
View the rest of this article and other foot conditions here.
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