Wild Horse Hoof Pattern Offers Help For Domestic Hoof Problems
By Gene Ovnicek
WITH THE BEST intentions in mind, many owners and trainers dictate hoof length, angle measurements, shoe types and weights with limited knowledge of the side effects they may cause.
Veterinarians and farriers often find these demands are unreasonable and are unwilling to compromise functional hoof shape and stance by allowing unnatural leverage forces on the limb. Seasoned veterans know well that in time, hoof distortion can occur as a result of these practices and eventual acute and chronic lameness can follow.
Our experiences with domestic horses, along with the many graphs, gauges and tools, have centered our focus on the external appearance of the hoof capsule when treating these horses. Reliance on these elements of hoof balance has altered our understanding of the horseís natural equation for balance.
Iíve had to look at this dilemma through 35 years of farrier experience and feel deeply responsible for my contribution to the problem. Knowing well that horsesí feet perform very well in their natural environment, I was encouraged to look at hoof balance and maintenance produced by the wild horse through the elements of their environment and life-style for possible truth and answers.
I was able to study wild horsesí feet closely through imprints I had acquired from a two-year research project done in 1986 and 1987. A description of my findings as well as a comparison to domestic horse experiences follows.
Question Of Balance
The appearance and weight distribution or balance of the equine foot have been the subject of much debate and opinion with most descriptions based on the appearance of the average domestic horse foot. The purpose of this study was to measure objectively the feet of wild horses, assuming that the natural process of hoof preparation may provide the most optimal form for proper function and soundness.
Differences in weight-bearing structures of the foot and in weight distribution in the anterior-posterior plane are quite dramatic between normal domestic horses and wild horses.
Wild horses rely on the solar portions of the foot to bear weight and support the third phalanx with little contribution by the wall. Hoof mass in wild horses is distributed one-third in front of the widest part, of the foot and two-thirds behind that point.
Specific applications of these differences to domestic horses, both those that are sound and particularly those that suffer from various forms of pathology, are presented.
Materials and Methods
Examined horses were assembled for Processing by Bureau of Land Management personnel at the Britton Springs work center near Lovell, Wyo., in the spring of 1986 and 1987. A total of 65 horses were examined. In both years, horses were restrained in lateral recumbency. The front feet were cleaned and brushed to remove all debris. A rigid, flat freshly painted surface was applied to the ground surface of a front foot. In 1986, a straight line was drawn from the central sulcus of the frog, anteriorly through the apex of the frog, continuing across the sole to the toe. The intersection of this line with the white line of the foot was used as a pivot point for a compass divider. The other point of the compass was used to note any difference in the distance to the most posterior weight bearing portion of each heel. Photographs were taken of the solar surface of the imprinted foot. A lateral view was then taken with a hoof gauge applied to the foot. At the same time, the rule on the hoof gauge was used to measure toe lengths and notes were made on the visual appearance of the coronary band and external hoof wall. Two distinct groups of horses were studied: one from a sandy, desert environment and the other from a prairie-sod environment. The foot evaluation procedure was modified in 1987 based on findings from the previous year. The imprints had revealed a consistent four-point pattern of contact with one point at each heel and one point on either side of center at the toe. In 1987. After the foot was imprinted, one line was drawn between the two toe imprints and two diagonal lines were drawn from one toe imprint to the opposite heel (Figure 1). Also in 1987, the pivot point of the compass divider was placed at the center of the true apex of the frog, which was identified by the removal of excess frog, if necessary. Again, this pivot point was used to compare the distance to each heel. Photographs, toe-length measurements and notes on the visual appearance of the coronet and wall were taken as in the 1986 project. The horses studied in 1987 originated in a high-desert environment with terrain consisting of shale and granite.
Toe length ranged from 2 5/8 inches (-6.7 cm) to 3 1/4 inches (-8.3 cm). The shortest toe lengths were present on horses from more abrasive terrain (2 5/8 to 2 7/8 inches) and the longest came from those originating in a sand environment (2 7/8 to 3 1/4 inches).
Those shaped by a sod environment were intermediate in length (2 3/4 to 3 inches).
Four imprint marks were consistently present on every foot- medial and lateral toe, and medial and lateral heel (Figure 1). The imprint marks at the toe were primarily on the sole side of the white line at 2 and 10 oíclock.
A hard callused area extended across the sole between the two toe imprints. This callused area of sole was the area of break-over because the hoof wall was rounded anteriorly.
The distance from the apex of the frog to the point of break-over ranged from 1 inch in small feet to 1 1/2 inches in the largest feet. No correlation between environment and point of break-over was noted.
Dorsal hoof-wall angle. Measured with a hoof gauge, was in the range of 57 to 68 degrees, 54 to 62 degrees and 51 to 57 degrees in horses originating from soft, sandy packed sod and gravel, and hard rock environments, respectively (Figure 2).
The distribution of hoof mass viewed from the solar surface was consistently one-third in front of the widest part of the foot and two-thirds behind this point. The hoof wall had surprisingly little contact with the imprint board. Horses from the sandy range had the deepest cup and the most hoof wall contact occurring at the heels and medial and lateral toe.
Conversely, horses from the rocky environment had virtually no hoof wall contact, but the frog, bars and toe callus all bore the imprint marks.
Although the length of heel varied greatly between environments, the functional hoof angle was very similar. The functional hoof angle is defined as the angle formed between the dorsal hoof wall and ground surface during weight bearing (Figure 2). Soil and organic material packs into the solar surface of the foot and may play an important role in weight distribution in all portions of the foot, especially the posterior two-thirds of the hoof. Toe lengths become shorter in harder, more abrasive terrain, and in no instance did toe length exceed 3 inches.
Four primary weight-bearing points were present in every foot, medial and lateral toe and medial and lateral heel.
The area of break-over was a callused ridge in the sole connecting the two imprints. This point of break-over ranged from 1 inch to 1 1/2 inches anterior to the apex of the frog.
The frog is fully loaded during weight bearing and the posterior portion was heavily callused, facilitating its function in weight bearing to a point behind or posterior to the heels in all terrains (Figure 2).
In the most abrasive terrain, the wall showed little or no contact with the flat imprint board. The major portion of foot mass was behind the widest part of the foot.
These findings have several implications in the way we prepare and shoe domestic horses and suggest a square toe with a break-over point 1 to 1 1/2 inches anterior to the tip of the frog is normal. With break-over occurring at this point, the majority (two-thirds) of weight bearing is born by the foot behind its widest point.
The fact that the sole, bars and frog are designed to be weight-bearing structures can be used to great advantage when dealing with pathologic conditions of the wall like laminitis, contracted heels, quarter cracks and the like. The soil packed in the foot may serve an important role in dispersing weight to the entire solar surface of the foot.
Change Of Thought
Putting into practice the information I had gathered required a major shift in thinking. The idea that the sole, bars and frog might play a major role in support of P3 (the coffin bone) instead of occupying a suspended state seemed scary but almost refreshing.
It has been common practice for farriers to remove, sculpture and minimize these areas of the foot. Doing so suggests that the wall bears the burden of total support of P3.
Fortunately there are many farriers who look differently on these structures and tread lightly with a hoof knife. Those who understand the importance of the natural foot structure have decided that those features look just fine the way they were intended.
It is refreshing to know that whomever designed the hoof did not make these parts by mistake after all. The fact that the sole, bars and frog have a function and possess the ability to respond rapidly to environmental changes suggest their presence are very important for support.
The wall, on the other hand, wears itself down in several ways to allow the surface below P3 the benefit of some support. Broken areas, quarter cracks, toe cracks and flares are all functions that allow the wall to be eliminated when either excessive growth or imbalance occurs.
Horseshoe manufacturers play an important part in how hooves are shaped. The simple fact is that most farriers use ready-made shoes and do not use a forge to alter shoes to front and rear patterns.
Iíd like to thank those manufacturers who are progressive in thinking and are willing to took at what is best for the horse. Shoes designed with good heel support and early break-over at the toe comply well with natural hoof form and function.
Thoroughbred Racing Plate Co. is currently marketing and manufacturing the World Racing Plate. Comments from consumers are abundant and positive. Many reports admit that these odd-looking shoes were applied to horses suffering from many types of lower limb pathology. These horses seem to improve from soreness while training continues. When imbalance (long-toe, low-heel syndrome) is addressed by use of the World Racing Plate, improved time, soundness and performance have been noted by the majority of those who have taken the chance and tried something that complies with natural form and function. Performance horses and track horses alike feel the benefits of the natural hoof pattern.
The Natural Model
There is currently a major shift in this industry to look more closely at the natural model for answers. Many skilled farriers have come to appreciate natural balance from the bottom of the foot. They have seen distortion and devastation occur when these parameters are not met.
Simply raising the heel to align the pastern with the dorsal surface of the hoof capsule with no regard for proper position of break-over or proper position of the heels ensures certain devastating effects on the soundness and performance of the equine athlete.
Those who have come to appreciate and are using these natural guidelines or some parameters closely related are finding positive results in soundness and performance.
It frees them from hoof gauges, charts and mechanical device dependency and offers a simple, back-to-nature solution that works well with the equine anatomy and physiology of the lower leg and hoof. This approach provides flexibility for farriers to deal with each horse as an individual, supporting their unique needs in either disease or performance situations.
The Normal Foot?
We as horsemen and equine professionals must seriously question our collective paradigm of the normal equine hoof. The normal foot we picture in our mindís eye, what we strive to create in clinical situations and what we use as a control in laboratory situations may not be normal at all.
Obviously the environment we place our horses in and the tasks we ask of them are far different than those that occur in the wild. However, the basic principles presented here are consistent in horses from a wide variety of conditions and, in my opinion, hold the key to understanding balance and shape for optimal form and function.