The equine foot is a miracle of engineering and a design that is unique in the animal kingdom. Other ungulates (animals that walk on their toes) have shock absorbing mechanisms ranging from a cloven hoof to the very soft and cushiony foot of an elephant, camel, rhino, etc.
Why the equine foot evolved the way it did is a bit of a mystery, but one clear thing is that the form of the horse is best suited to brief spurts of speed while the vast majority of the time of the horse is spent walking and grazing.
While feral horses may cover much more total mileage in a day than a domestic horse, the time they spend at anything other than a walk may be very different. The hour or so a day working a stall-kept horse may be far less total time than a feral horse spends moving around. The domesticated horses spend much more time in a trot or canter at higher speeds and therefore there is higher impact on the hoof.
Hooves Vs. Lameness
It has been estimated that 60% to 80% of lameness issues in horses originate in the hoof. If you also include issues found higher in the leg that are influenced by hoof form and imbalances, it is likely to be well over 90%.
Hoof issues have three main influences - genetic, trimming/mechanical and nutritional - not necessarily in that order. There's nothing we can do about genetic influences, but these make it all the more important to make sure that mechanical and nutritional problems are not an issue.
The hoof wall should hug the internal structures like a sock hugs a human foot. If it doesn't, consequences for movement and soundness range from the equivalent of trying to move in a clown-foot shoe to Asian foot binding - and many problems in between.
The purposes of this article doesn't include the details of trimming, but suffice it to say that this is a critical component of keeping hooves healthy, regardless of whether they are shod or not.
Avoid Nutritional Deficiencies
Because the hoof is so metabolically active and constantly growing, nutritional deficiencies often are evident in the hoof. These include slow growth, cracking, chipping, thin and brittle walls and increased susceptibility to abscesses and thrush.
Inadequate protein in general, or a deficiency of methionine, limits the ability to produce the hoof wall's structural protein, keratin. Also necessary for keratin production are vitamin B6 and folic acid. Biotin has also been shown to be important for both good hoof growth and quality. On the mineral front, calcium, zinc and copper are particularly important for the functioning of the enzymes needed to produce keratin and infection resistance.
Often overlooked, fat is very important to hoof health and integrity. The various fats and waxes fill the spaces between the keratinocytes. They give the outer layer of a healthy hoof a naturally slick feel and shine. The outermost layer of the hoof wall (stratum externum, aka periople) also contains a variety of fats and waxes, as does the "hard" or dead portion of the hoof wall in general. When present in correct amounts in an unbroken layer, these layers of tissue seal moisture into the deeper hoof structures and seal water out.
Fatty Acids Needed
It is known that supplementing fat can change the fatty composition in the hoof, and often has a visibly obvious beneficial effect on the feet. While the horse is capable of synthesizing the various types of fats found in the hoof wall, horses eating hay rather than fresh vegetation are consuming 50% less fat. Be sure to include the omega-6 and omega-3 fatty acids as these must come from the diet. Omega-6 is also important for resisting infection.
Faulty nutrition isn't the only factor in hoof-quality problems, but it's a big player. While genetics and faulty care are also involved, adequate nutrition can make the difference between the hoof with a potential for problems, and one that actually develops them.