ASSESSING THE HORSE - Hoof
What is a Strong Hoof?
In order to identify a distorted or weak hoof, first it is necessary to know what is normal for a hoof so that meaningful comparisons can be made. What does a normal, functional hoof look like? How does it work? There is an abundance of information and photographs available in literature and on the internet detailing deformed or unsound hoof forms. There are also some photographs available of wild or feral horse feet from various parts of the world. Finding images of domestic horse feet that are consistently strong with no need for protection from boots on any terrain or in any weather conditions is a little more challenging. This page provides a brief overview of what to look for in a strong, working domestic foot.
The hoof images below are from three domestic horses with strong, functional feet. No hoof protection is ever needed, truly 'gravelproof'. To maintain their strong feet, all three horses have been fed, for many years, the same diet outlined on this website.
Click on any image to see a larger version
A CLOSER LOOK AT WHAT MAKES A STRONG EQUINE FOOT
Short hoof capsule with no wall flaring and smooth profile over pastern-coronet junction.
Swelling around coronet indicating stress on soft tissue.
Photo courtesy D. Lillington
Tubules diverging at ground level equates to a structurally strong cone-shaped hoof.
Tubules converging at ground level equates to a structurally weak inverted cone-shaped hoof.
Photo courtesy T. Bauer
The heels are wide apart with thick lateral cartilages and digital cushion. The back-of-the-foot appears 'full'.
The sole, frog and bars of this foot have not been trimmed in years; the concave sole profile has developed naturally.
The heels are pointing inwards with weak lateral cartilages and thin digital cushion. The back-of-the-foot appears 'empty'.
The sole is flat with uneven areas of callousing and significant wall separation.
The Importance of the Caudal Hoof (Back-of-the-Foot)
The health of the hoof cannot be assessed by external appearance or form alone. The optimal function of internal hoof structures is a major factor in how the horse moves at all paces over varied terrain. Research over two decades by Prof Robert Bowker at Michigan State University has shown the equine foot has an inbuilt mechanism for absorbing concussion during movement. An important part of that mechanism is the lateral cartilages (LC), and digital cushion (DC) which is comprised of fatty tissue, fibrous tissue and fibrocartilage.
For a full explanation of how the equine foot works, go to Prof Bowker's website:
The DC is a wedge-shaped mass of material located inside the hoof, above the frog and below the back of the coffin bone. The thin end of the DC wedge starts beneath the middle of the coffin bone, extending back to the heel bulbs. The top of the DC can be felt as the soft depression between the two cartilages as shown in this photo.
As the hoof is placed on the ground during each step, the DC compresses as it aborbs shock from impact thus minimizing any potential damage to bones and joints as shock waves travel through the skeleton.
It is clear from the dissection photo above that there is no protective DC below the front half of the coffin bone. It is therefore evident that in movement the hoof is best suited to land on the ground with the heel being placed down first, followed by the toe. If the toe hits the ground first there is very little soft tissue to dampen the jarring of impact.
The DCs on a newborn foal are very soft, mostly fatty tissue, but that is adequate to support the light weight of the foal as he bounces around in play. As the youngster grows and becomes heavier, the DCs start to develop fibrous tissue and then fibrocartilage that provides substance and elasticity to the DCs. By the time the horse is fully mature at 7 or 8 years of age the DCs are wide and thick with a firm but elastic texture. Growth of DC tissue is generated by the constant expansion and contraction, compression and rebounding, of the hoof with each step but only if the heel is the first point of contact with the ground. When the toe lands first, the DC becomes redundant so does not receive the stimulation necessary to develop and/or maintain the fibrocartilage within, resulting in an adult horse with the soft DCs of a foal.
What could cause a horse to move with a toe-strike?
Occasions when it is appropriate for a horse to move with a toe-strike are discussed on the MOVEMENT main page but a great many domestic horses move with a consistently toe-striking gait. Although the resulting jarring would be uncomfortable, there are numerous reasons why a horse will do this, including any one or all of the following:
a) Soft, foal-like DCs do not give adequate protection to the sensitive areas in the back of the foot; this makes heel impact more painful than toe impact.
b) Many horses live in regions that were formerly used for dairying or livestock fattening and therefore are grazing pastures with predominantly high-sugar grass species. The correlation between high sugar intake and laminitis is well documented. In non-acute cases of laminitis, rotation of the pedal bone may not occur, but the lamella connection between the bone and the hoof wall is weakened, allowing the bone to sink lower down within the hoof. This results in the sole bearing a greater proportion of the weight of the entire horse than if the bone is held higher up within the hoof. The extra weight on the sole can crush the soft tissues and blood vessels that lie between the bone and the inside of the sole, producing an inflammatory response and reducing growth of healthy sole material. The sole progressively thins and the horse becomes increasingly footsore on anything but the softest ground. Shorter steps become less painful than longer steps as each individual foot bears weight for a shorter period of time. A short step compels the horse to land on his toe as there has not been time for the foot to complete its flight-arc for a heel landing.
c) A horse feeling foot discomfort from mild lamella inflammation may try to minimize the pull of the deep digital flexor tendon (DDFT) on the underside of the pedal bone by moving with short steps. The longer the step length, the greater the force exerted on the area of bone where the DDFT attaches.
d) A horse who is holding his body in a braced posture where the topline muscles are maintained in a contracted state will move with a shorter, choppy gait and be more likely to land flat or with the toe first.
What can done to help a horse move with a heel-strike?
Given the right conditions, it is possible for an adult horse of any age to increase the depth and width of his DCs. To do this, his feet must feel comfortable enough to allow him to consistently load his heels with each step. Ideally, horses’ living conditions need to mimic the open ranges with low-sugar native grasses they evolved to graze. Realistically, very few owners of domestic horses are able to provide an environment with any similarity to that of wild or feral horses, therefore managing diet is crucial to hoof health when horses are kept on small, high-sugar pastures.
It has been found that supplementation with certain minerals can assist some horses to live healthily whilst having unlimited access to less than ideal pastures. An example of this is Rory, a 20 yr old thoroughbred gelding with a history of poor hoof function, laminitis and Cushing’s disease. Rory was shod until 11 years of age by which time his feet had deteriorated so much they would not hold a shoe. Appropriate trimming improved his bare feet to the extent he could work on soft ground such as sand or grass but his DCs remained thin and soft; he did not consistently place his heels down first and was frequently tender-footed on hard or gravelly surfaces. Some years later supplements were added to Rory’s diet, including magnesium and then chromium.
As can be seen from these photographs, Rory’s DCs improved considerably over an 8-month period in 2009 when he was 19 years old. He was then able trot and canter comfortably, with a clear heel-first landing, on very hard ground.
This happened purely through dietary supplement adjustments; he was not in work and there were no changes to basic diet, 24/7 grazing, hoof trim, exercise or living conditions.
to read 'Rory's Story'
How much digital cushion does a horse need?
The easy answer is that 'more is better'. The chestnut TB, Rory, has significantly increased the dimensions of his digital cushions and improved texture from soft to a gelpad-like firmness. This is enough for the terrain he lives and moves on, and the light work he is asked to do. Although his feet have improved substantially, they are not as strong as those of his two paddock companions who have never been shod or had any major hoof distortions. Compare the photographs at the top of this page to see how strong a domestic hoof can be.
Recording changes in DC dimensions is a useful way to track changes in each individual horse. Approximate measurements can easily be taken, as shown here. Place a steel ruler across the heel buttresses, then position the calipers so the lower prong is on the steel ruler, centred below the frog, while the upper prong just touches the highest area above where the DC can be felt externally. Remove the calipers to measure the distance between the two prongs. It is important to ensure the pastern joints are fully extended (hanging loosely when the fetlock is supported from beneath). If any of the joints are even slightly flexed, an inaccurate measurement will be taken.
For the sake of consistency, the best time to measure is always immediately after a trim.
Generally, larger horses will have less DC per 100kg of bodyweight than smaller horses and will therefore be more susceptible to hoof problems. The chart below summarises digital cushion measurements for 12 Shetland ponies and 12 Draft horses, comparing body weight and height.
SOME DIGITAL CUSHION DATA
From Sheltands . . .
Average DC depth
Average DC depth
per 100 kg bodyweight
. . . to Shires
Average DC depth
Average DC depth
per 100 kg bodyweight
12 ponies, 12 drafts, Winter 2010, P. Moore
These are the same three horses shown at the top of this page. Even the older TB, Rory, shown on the right below, has acquired a strong foot with more depth of digital cushion than the average draft horse.
15 yrs 16.0 h 520 kg
Av. DC/frog depth
Fore 75 mm
Hind 65 mm
Av./100 kg 14 mm
9 yrs 15.3 h 600 kg
Av. DC/frog depth
Fore 67 mm
Hind 57 mm
Av./100 kg 11 mm
22 yrs 16.1 h 560 kg
Av. DC/frog depth
Fore 57 mm
Hind 50 mm
Av./100 kg 10 mm
The digital cushion can act as a mirror that reflects
how the horse has been using his body.
Good depth, firm texture DCs on all 4 feet
Comfortable to heel-strike, freely moving body
Hind DCs thinner & softer than on front feet
Weight taken on forehand, not using h.quarters
Front DCs thinner & softer than on hind feet
Thin, soft DCs on all 4 feet
Weight taken on hindquarters
This horse needs a lot of help
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