Tag Archives: horse hoof

The totally underrated Digital Cushion: a horse owner’s guide

 

The digital cushion is  a major component of the  circulation and shock dissipation apparatus of the horse’s digit. It is a  elastic, wedge shaped mass composed of a fibrous fatty tissue that has the consistency varying between your earlobe and nose depending on it’s health. Ideally, the digital cushion takes up the majority of the rear 1/2 of the  hoof. It’s nestled underneath the deep flexor tendon, between the lateral cartilages, and above the frog.  The DC can be felt by pressing  between the bulbs of the heel. 

The DC  has sheet like ligaments that stretch from one  lateral cartilage to the one opposite, allowing for independent movement of the sides of the foot.  The digital tarus, part of the DC, originates from the underside of the coffin bone and deep digital flexor tendon and sends bands of fibrous tissue toward the heels  creating a a biologic lattice for the vasculature of the back half of the foot. There are also a series of trampoline-like ligaments traversing the inner surface of the frog, facilitating it’s expansion and contraction.

palmer hoof digital cushion

Horses have many ways to dissipate the concussion of moving at speed.  One way is by hemo-dynamic shock absorption in which the digital cushion plays an integral part. Let me explain:

During the swing phase of stride, blood is pulled into the extremities via centrifugal force. Upon the hoof landing, the fetlock descends. This drop causes the veins to close, trapping the blood within the hoof and dissipating shock like a waterbed. Much of this trapped blood is  in the matrix of tiny veins and capillaries running amongst the sub structures of the DC.  As the horse passes over the hoof, the fetlock rises and the blood-way is open. This built up pressure then shoots the de-oxygenated blood back up the leg, returned to the body and heart.

Venogram of the digit

 

It is important for the horseman to know that there is a wide range of variability when comparing DC between good and weaker footed horses. In a strong hoof, the ligaments of the DC are much thicker and the digital tarsus will have numerous fibrous connections .  The reasons for this are thought to be due to the presence of a highly adaptable myxoid  tissue in the region. Myxoid tissue is very adaptable and can become fibrous or cartilage. It is thought that the environment and how the foot is trimmed and/or shod can contribute to the makings of a robust foot.

Util recently, most discussions on hoof lameness were  limited to deterioration or injury to the navicular bone,  coffin bone, the deep flexor tendon, the navicular bursa, distal sesmodian (collateral) ligaments or the coffin joint capsule itself.

It is my belief that these structures are often damaged due to lack of a properly functioning digital cushion. Further, I believe that much of the objective of  best farriery practices is to be aware of the health of this underrated structure. In my practical experience I have come to believe that digital cushion is very adaptable, even in mature horses or ones with already compromised hooves, Horses that are well managed with plenty of exercise over varied terrain and shod or trimmed in a balanced manner will tend to have a more fibrous DC than horses that are kept up and not shod or trimmed well.

For more information on the Digital Cushion, I would like to recommend Epona TV’s 6 part series featuring Dr. Bowker.

 

 

Structures of the Hoof

 

palmar-foot-drawing-labeled
click image to enlarge

 

 

I hope this will help  make conversations about your horses  hooves more effective. Some books do not go into great detail of farrier terminology as much of this was news to me as a horseperson entering farrier school. These are terms I learned which seem to be commonly accepted.

Hoof Wall: This is the most obvious and largest external structure. It is produced at the coronary band and grows distally, meaning  towards the ground. The farrier mostly trims hoof wall hopefully and if shod, it is what the shoe is secured to.

The majority of the horses, shod or barefoot, weight is supported by the hoof wall. It is strong, durable yet surprisingly flexible in order to accommodate for the constant expansion and contraction involved in locomotion.

Heel: I consider the heel as an extension of the hoof wall. The wall actually bends inwards sharply next to each side of the frog. Those sharp “V”  corners form heels. You can be more specific if you are referring to one or the other by using the term medial, lateral or inside, outside. Left and right become too complicated when dealing with horse feet.

hoof capsule, notice how the wall folds inwards and forward to create the heel and bars.
hoof capsule, notice how the wall folds inwards and forward to create the heel and bars.

Bars: the bars are a continuation of the hoof wall that protrude from the heels towards, while becoming less prominent  as they near the tip of the frog.

The tapered bars become increasingly more weight bearing  as the foot is loaded. As the foot expands the bars are pushed towards the ground to aid in shock absorption.

Sole: this is the horn that covers the majority of the ground bearing surface of the foot. It is constantly  produced and  within the hoof capsule and self exfoliating. The ideal sole is concave and thick enough to protect the coffin bone, blood supply and other sensitive structures just millimeters above.

The sole is not considered load bearing, although in horses that are kept barefoot the sole with thicken to the extent that there may be ground contact.

horse at 6 weeks since last trim
horse at 6 weeks since last trim. Good management has resulted in a strong foot with a thick sole, strong straight hoof wall and a massive frog.

White Line: a bit of a misnomer, the white line is a yellowish , insensitive substance that is sandwiched between the hoof wall; including heels and bars, and the sole. It may be difficult to see the white line unless the foot is clean and recently trimmed.

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fresh hoof!

 

The white line is produced internally peripheral edge of the coffin bone and lies beneath the laminae and fills the void that would be left between the sole and hoof wall. You could think of it as  a border and bond between the sole and wall.

Nails are driven into the white line ideally and exit via the hoof wall.

The white line is a load bearing structure except for the area called…

Seat of Corn: sometimes called the seat of heel. This is an area not a structure. This is the point of the foot where the hoof wall folds back on itself. That juncture is especially prone to irritation  in some modern horses and a lameness caused by this is called a corn.

heel abscess or “corn” in the seat of corn region on this neglected foot. The frog has become non weight bearing because the wall had become excessively long causing it to atrophy and shrink as well.

Frog: this is the triangle pad of moist and pliable horn situated between the heels. The frog aids in traction,  shock absorption and circulation.

The frog, like the other structures are continually produced by a corresponding sensitive structure .

The frog is a weight bearing structure.

Commisures or Medial and Lateral Frog Sulci: these are the two groves formed by the joining of the frog and the bar. This is the “V” shaped area that is cleaned with a hoof pick.

Frog cleft or Central Sulci of the Frog: This is the grove that is made between the left and the right side of the frog, Some horses are prone to getting a deep thrush here that can go undetected.

I hope this helps you say what you mean, hopefully I will be adding to this in the very near future.

 

 

 

to shoe or not to shoe?

 

There are a few factors that you should take into account when determining the hoof care needs of and individual.  Ask yourself:

What are you going to do with this horse? 

A lot of times the answer is not much. If the horse is going to be used lightly on easy footing like sand or grass, the horse may be fine shoeless. On the other hand, if your plans include extensive trail riding or the footing you have is abrasive, I would recommend having some hoof protection.

Competition horses benefit from horseshoes because of the increased traction can give an edge to the horse. In horse racing, shoeing choices are made known so the bettors will have more information to base their wagering decisions on.

People who show or ride their horses away from home may need shoes as the venues may have unpredictable footing.

shoes can give horses extra traction
adding studs shoes can give horses extra traction
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high performance shoes can make the difference in speed events

 

lightweight race shoe
lightweight “queens plate” with no toe grab for flat racing , notice how the frog takes up a third of the area. A big healthy frog indicates good circulation and fuction of the foot

 

What is the quality of the horn?

The hoof wall is made of horn. The horn can be thought of as lots of tiny “straws” starting at the top of the hoof and growing towards the ground. Horses with horn that grows pretty much straight, without flaring (“platter foot”) or bending at the heels (“crushed heels”) are candidates for barefoot.

This is not a static state either, once hoof imbalances are addressed and a new growth pattern is established by a few cycles of timely shoeing  the barefoot option may be asked again. A goal of mine when shoeing any horse is bringing the foot to equilibrium with or without shoes.

Horses of all breeds can be successfully kept barefoot but ponies, gaited horses, drafts, appaloosas, paint and mixed breed horses usually have inherently good hoof quality.

plz pass the biotin, I need some shoes!
plz pass the biotin says this “well bred” QH broodmare, I need some shoes!
rock crushing appy feet
rock crushing appy feet , the stripping in this foot shoe that the horn tubules are growing  uniformly

Is growth exceeding wear?

If the horse grows two nipper round of hoof in four weeks, it may not get them nailed back on. The hoof is excellent and gives excellent traction on a variety of surfaces. A horse like this may be able to perform at high levels without shoes.

hmm, wear exceeding growth...not today!
hmm, wear exceeding growth…not today!

 

Does the horse have a condition that the shoes help alleviate? 

Therapeutic horseshoes can be of great value to the unsound animal. Veterinarians will recommend shoeing protocols designed to help the limb function more normally. Wedge heels can decrease pull from certain tendons, leather pads can protect a thin-soled foot and modifications to a basic shoe will help ease breakover (the phase of stride where the foot rolls off the ground). Good horseshoeing can enhance performance.

2014 11 05_0213
injured sole will love a shoe and pad to protect it

 

pad to protect sole
pad to protect sole

Some horses will transition without missing a beat when taken out of shoes, some will require a little time to get used to it especially while the old nail holes grow down. Most performance horses need shoes because of the demands upon them.

I recommend evaluating your current situation and discussing the options with your farrier or hoofcare provider.

strong and straight horn growth  and a concave sole are an effect of good genetics and regular hoof care.
strong and straight horn growth and a concave sole are an effect of good genetics and regular hoof care.