Healthy Feet: Selection and Care

The following information was given at a Seminar on Equine Nutrition and Health sponsored in part by the Virginia Horse Industry. It was held on October 17, 2008 at The Middleburg Agricultural Research and Extension (MARE) Center, Middleburg, Virginia. The following is being posted on HorseHints with the permission of the lecturer. This Seminar was beyond outstanding. My husband, Bill and I, feel so fortunate to have been able to attend.

"No matter how talented a horse is, if its feet are not good, it will never reach its potential (performance or longevity). The keys to strong, healthy feet are good conformation and proper foot care. The purpose of this presentation is to review the "foot factors" which will optimize a horse's performance and reduce the likelihood of lameness problems.

The term hoof refers to the hoof wall, sole and frog. The hoof wall is thickest at the toe, and becomes thinner and more elastic toward the heel. The inside hoof wall is usually straighter (less curved) and more upright (steeper) than outside hoof wall.

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The term foot refers to the hoof and all of the structures within it. Important structures within the hoof include the corium (dermis), coffin bone, coffin joint, navicular bone and bursa, and the deep digital flexor tendon. The corium/dermis (often referred to as the quick) is the sensitive (contains nerve endings), blood-rich tissue that lines the inside of the hoof. The corium/dermis produces and nourishes the hoof, and also serves to attach the coffin bone to the hoof. Projections from the corium/dermis interlock with projections from the inner hoof wall forming an extremely strong flexible bond. The projections are referred to as lamellae and the region as the lamina. In the horse the lamellae have secondary projections (secondary lamellae) which serve to increase the surface area of attachment. The coffin bone (and therefore the weight of the horse) is suspended within the hoof by this laminar attachment.

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The hoof wall grows from the coronary band downward, at a rate of about 6 to 10 mm (1/3 inch) per month. Hoof growth is usually the slowest in the winter months and the fastest during the spring and summer. Regular exercise promotes hoof growth. There does not appear to be a difference in the growth rate or strength between pigmented and non pigmented hooves.

Individual horses can be characterized as "slow or fast growers." Horses with slow hoof growth rate can present shoeing problems. If the hoof wall in the nailing area is not turned over rapidly enough, the farrier will have to alter the paths of his nails in order to avoid the old nail holes. This may alter the "tightness" of the shoes, predisposing to premature loosening or loss of shoes. Owners should attempt to evaluate the rate of hoof growth when considering purchase of a new horse. Ideally, the nail holes from the previous shoeing should be near the bearing surface of the hoof wall and 12 to 20 mm below the new nail holes.

Goof foot conformation is critical! The hooves should be of sufficient size for the horse's body weight. Small hooves increase the force per unit area of hoof and predispose to concussion related lameness. The hoof wall should be thick enough to provide an adequate base of support and to allow horseshoes to be nailed on safely and securely. The hoof should be wider at the ground surface than at the coronary band to allow normal hoof movement/expansion. The inside and outside walls of the hoof should bear weight evenly. The sole should be slightly concave and not bear weight.

The angle of the hoof is considered correct when the hoof and pastern are in alignment (the slope of the front of the hoof wall should match the slope of the pastern). This is referred to as a matched hoof-pastern axis. This alignment is best viewed from the side of the horse, with the horse standing squarely on a hard level surface. This means that each horse has its own "ideal" hoof angles. The angle of the hoof at the heel should ideally be parallel to the angle at the toe.

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With this guideline, the normal angle in the fore hooves averages about 54 degrees, and in the hind hooves, it averages around 56 degrees. Alterations of the hoof angle away from a position of alignment with the pastern axis are associated with changes in the angulation of the coffin joint and, consequently, the pastern segment. If the hoof angle is lowered, the coffin joint becomes more extended, and the pastern segment becomes more upright. Low hoof angles increase the weight supported by the heel region (navicular region!) and makes breakover more difficult. Conversely, as the hoof angle is raised, the coffin joint becomes more flexed, and the pastern segment becomes more sloped (and the fetlock drops).

The main reason that we apply shoes to horses' feet is to protect the hooves from excessive wear which would result in lameness. Not all horses need shoes! A properly trimmed, unshod hoof is cheaper and easier to maintain than a shod hoof. Barefoot horses are safer to themselves, other horses, and humans than are shod horses. Shoeing can negatively affect hoof growth and amplify the forces on the foot at impact and breakover. However, many domestic horses (most performance horses) are housed or worked in environments in which hoof wear exceeds hoof growth, making application of horseshoes a necessity. Other reasons for shoeing horses include providing traction, to correct or influence the stance and/or gait of a horse, and to correct or improve abnormal or pathological conditions of the feet and legs. Young horses should go barefoot until factors indicate that they need to be shod.

Proper (correct) trimming and shoeing techniques are important for maintaining soundness and maximizing performance. The hooves should be trimmed to establish matched hoof-pastern axes (the slope of the front of the hoof wall should match the slope of the pastern) and so that the inside and outside walls of the hooves bear weight evenly. Shoes should be set "full" (to allow for hoof movement and growth) and "long" (to provide support and to allow for hoof growth. The toe of the shoes may be "rolled" or "rockered" to ease breakover (the point of breakover should be approximately 1.5 inches in front of the apex of the frog). Nails should ideally be placed only in the front portion of the hoof so as not to inhibit the natural movement of the hoof (spreading of the heels as the hoof bears weight). The shoe should rest only on the hoof wall (and not the sole). The rate of growth and wear of the individual horse's hooves, and the use of the horse determine the frequency of trimming/shoeing.

Several environmental factors can affect hoof health. The combination of urine and manure provides a perfect medium for the growth of bacteria and fungi that can cause the breakdown of hoof wall ("white line disease"). The excessive moisture and irritating breakdown products of urine and manure may also result in direct injury to the hoof wall.

The effects of repeated wet/dry conditions (environmental or management related) can be especially harmful to hooves. Repeated wet/dry conditions causes the hooves to go through stressful moisture expansion/contraction cycles. These cycles lead to cracking of the hoof wall and white line. Dirt and microbial invasion of these cracks can lead to undermining and separation of the hoof wall, white line disease, and subsolar abscesses.

Biography - Dr. Scott Pleasant, DVM, MS, D-ACVS, Virginia-Maryland Regional College of Veterinary Medicine, Blacksburg, VA

Dr. Pleasant is an Associate Professor in the Department of Large Animal Clinical Sciences at the Virginia - Maryland Regional College of Veterinary Medicine (VMRCVM), Virginia Tech. Dr. Pleasant has been a faculty member at VMRCVM since 1991 and is board certified in veterinary surgery by the American College of Veterinary Surgeons. He currently severs as a member of the College's Equine Field Service Section and as the College's Equine Extension Specialist. His clinical and research interests include equine lameness and podiatry."