If, according to an old English proverb, the eyes are the windows to the soul, then for horses and humans the nails and hooves
may well be the windows to inner health or medical problems.
Careful and close attention to the exterior hoof capsule and related anatomical structures often can provide a wealth of information
concerning environmental factors, nutrition, infectious diseases, toxicities, deficiencies and farrier care.
In their 1999 Manual of Equine Dermatology, Dr. R.Pascoe and D. Knottenbelt address this in the section on hoof problems. "Inevitably some disorders of the hoof have
profound implications for the welfare and health of the animal itself," the doctors write.
The hoof and coronary band are particularly useful to the clinician and, according to Pascoe and Knottenbelt, "sometimes provide
important information on underlying systemic or generalized disease processes and, in some cases, the particular condition
may then only become manifest when the hoof wall shows abnormal growth patterns."
Photo 1: Endurance-horse hoof ridges and close-up of hoof.
Dr. Andrew Parks, a surgeon at the College of Veterinary Medicine at the University of Georgia and a member of the International
Horseshoeing Hall of Fame, agrees with the benefits of careful hoof evaluation.
Photo 2: Endurance-horse hoof ridges and close-up of hoof.
"The hoof offers (the clinician) clues that are not present elsewhere," he says, "yet the rigid hoof capsule inhibits basic
palpation of the structures within the foot." And the usually pigmented surface does not allow veterinarians access to as
much information as can be obtained from human nails. "Therefore," Parks advises, "it is important to develop an ability to
'read' the hoof capsule (which seems to be a life-long process)."
Clinicians should have a good understanding of the structure and function of the hoof capsule and use abnormalities in growth
and appearance to gain possible insight into systemic conditions and diseases. The hoof is simply too good a "window" not
to utilize the view.
Composition and pigment
The hoof is a modified cornified epithelium, and is approximately 25 percent water. It is composed of three layers.
The first, or outer, layer is the relatively thin periople. The middle layer is the thickest and comprises the bulk of the
hoof. Horses with dark or striated hooves have their pigment located in this middle layer and there is no difference in structure
or thickness between pigmented and non-pigmented hooves. It is more likely that oft-repeated tales about horses with white
hooves having weaker feet and more hoof problems have more basis in the genetics that might relate some weak-hooved horses
than in any variation in hoof structure.
Photo 3: Diagonal stress lines.
The third, or inner, layer is the laminar layer that forms the epidermal connection to the dermal laminae below. Blood is
supplied to these various layers by corresponding layers of modified vascular tissue. The periopic corium, coronary corium
and laminar corium provide nutrition and vascular support to the hoof wall.
The generally accepted rate of hoof growth is 1 cm monthly for a healthy horse in a moderate environment receiving good nutrition.
Deviations or extremes in numerous factors can seriously affect hoof growth and its ability to heal and regenerate.