The Wild Horse's Foot
2001 - 14th Annual Bluegrass Laminitis Symposium Notes
The Wild Horse's Foot
Written and presented January 2001 by R.F. (Ric) Redden, DVM
(If you would like to learn about adopting a wild horse or burro, click here.)
I envied individuals who had the opportunity to study the feet of wild horses. So in January 2000, I launched a very serious project designed to record the radiographic and gross anatomical data in regard to wild horse feet.
1. Determine if wild horse foals and weanlings develop PIII fractures along the parietal groove that are frequently found inlight breed domestic horses, especially Thoroughbred foals.
2. Develop a range of normal radiographic parameters; horn-lamellar zone, toe - heel angles, sole depth, palmar angle, relationship of the extensor process with the top of the hoof wall and digital breakover.
3. Record the incidence of club feet (all grades) in young and mature horses.
4. Establish a range of normal contrast pattern in the digit using a venogram.
5. Collect a significant number of foot molds for further study.
6. Record angular deformities.
To my knowledge there has been only one radiographic study on live wild horses. (ref. accomplished with a turn table chute).
The first group of horses was gathered just south of Las Vegas four days prior to my examination. Using Ketamine and Rompun to sedate the horses, foot molds were obtained and radiographs taken. Views include lateral, AP, and 65 degree DP views. With the assistance of Dr. Tom Hartgrove and the Bureau of Land Management, we were able to study eight individual cases. All were more than one year old, no pathological lesions were observed, and none presented with club feet or abnormal angular deformities. All were in good flesh, but they appeared thin compared to domestic standards. Regardless, they all seemed healthy and sound, with a superb protective attitude.
The following is a basic summary of the radiographic soft-tissue parameters:
1. Horn - lamellar zone range
(20/20 mm. - 25/25 mm., majority 25/25 mm.).
2. Sole depth (15 mm. average).
3. Palmar angle (zero degrees).
4. Digital breakover distance (zero to 10 mm.).
5. Extensor process/top of hoof wall (ranged from zero to 10 mm.).
6. Toe angles (range 50 to 59 degrees, average 55 degrees).
7. Heel tubule angle (40 degrees).
8. Toe length (hair to breakover)
(range 2 to 2 1/2 inches, average 2 1/4).
9. Horn height in the center of the foot (1 1/2 to 2 inches, average 1 3/4 inch).
10. Foot size (3 3/4 x 4 W/L 4 1/2 x 5).
NOTES OF INTEREST:
This was a moving experience to say the least. Being the first to ever touch the feet of this small herd and to feel the strong message of Mother Nature was very enlightening and a catalyst for my project. I was surprised to find very short hoof capsules, yet all had thick, protective soles. The soles appeared burnished and fused with the frog which was hardly noticeable. There was only a slight mention of a medial - lateral sulcus. The characteristic shape and size of PIII varies considerably from that of most domestic horses. The apex is more blunt and the solar surface is more convex along the wings as viewed from the lateral radiographs. It is smaller in relation to hoof size than seen with the domestic horse.
The palmar angles are basically zero degrees verses three-five degrees for front feet and five to eight degrees for hind feet (ref. Verschooten). The horn - lamellar zones measured 25 mm on most mature horses verses 15 mm for the light breed domestic horse. The endodermal/ectodermal junction measured 7.5 mm from the face of the bone. The horn - lamellar zone was 1 - 1 with all young feet, only those three years or older exhibited the thicker wall characteristics. The front and rear feet all exhibited a similar breakover/heel-load surface. The wall along the ground surface had a very smooth radius that was void of any sharp edges. All feet were worn smooth with no signs of weak walls or broken out horn.
January 11, 2000 Second herd consisting of 1500 horses. This was simply a drive through and walk through examination.
This herd contained 600 yearlings and five newborn foals, with the balance being older horses. Radiographs, venograms, photos, and foot molds taken on 22 cases consisting of:
Two mature mares with foals.
Seven mature horses.
Some of these cases had been in captivity 30 to 45 days prior to examination. Noticeable hoof growth and pattern changes were evident in all cases held 30 days or longer.
Assistance was provided by Dr. Joe Coli, the Bureau of Land Management at Palomino Valley, Jim Stewart, Bernard Pelletier, and John Sligh.
NOTES OF INTEREST:
All feet exhibited a similar breakover/heel-load pattern even when showing signs of excessive growth.
Venograms were more difficult to inject than domestic feet as the intravascular pressure seemed much greater, regardless of age. Flow patterns were similar to the domestic horse but there appeared to be a smaller number of vessels. All revealed a significant reduction of contrast volume, as well as the number of vessels.
No club feet were observed in the entire herd, but two yearlings had very upright pasterns in the rear. These cases were on their toes with their heels off the ground. They also presented with very tight, contracted heels.
No varus deformities presented. Valgus deformities when present were seen as low grade 1/5.
There were no PIII parietal groove fractures in the yearlings examined. Six feet had a grain size lesion in the area where the parietal fracture occurs in light breeds.
Bureau of Land Management reported that they would see a few abscessed feet following a tough gather that required the horses to travel long distances over rough terrain. This would also cause an occasional stone puncture to the sole. All horses were gathered by helicopter and trailered to the holding center.
NOTES OF INTEREST:
Foals use their long tattered mane as a means of direct communication. The typical mouthing exhibited in all foals appears to be a direct line of communication. The large hair balls hanging off the shoulders of the mares was a security blanket for these babies.
When the mares were anesthetized the foals stood absolutely still and made no noise even though they could not see their mothers.
Mares with foals were thin but bagged up well. All vulvas were in a perpendicular plane to the ground. None dropped over the pelvic brim regardless of age or weight.
This was very interesting as most domestic mares soon lose tone and have to be sutured.
Mares had week old foals by their side, January 11, 2000. One foal was born the night before I arrived and was found dead the following morning. Examining the feet of this foal I was surprised to find no feather, but it had a well-formed sole, frog and wall in less than 24 hours. The typical feather seen in domestic foals for several days after birth would make these wild foals more vulnerable to predators. How has this genetic change occurred? We need to know. I adopted three yearlings and shipped them to my farm for further examination.
July, 2000 Third Herd, Tonopah, Nevada:
Approximately 250 horses were gathered, sexed, aged and culled for adoption, 47 foals that were eligible for adoption were taken from their mares; some were as young as a few weeks old. The very young ones were taken to a volunteer nursery for bottle and bucket feeding. This heard consisted of approximately 35 stallions, 47 foals, and 30 to 40 yearlings. The balance of the herd was mares.
Most mares were 20 years old or more. The majority had foals or were showing signs of pregnancy. Most lactating mares were ribby but bagged up well. There is more grass growing on the paper I am writing this report on than can be found on 100 acres of their natural habitat.
The older mares develop weak suspensories behind, a very straight hock and a steep, bull nose foot. With more in-depth study, the approximate age can be determined by simply observing the hind limb conformation.
No sloping, tipped forward vulvas were noted.
No true club feet nor varus deformities.
Several chronic foot injuries were noted, and they appeared to be old lacerations. A few presented with blown out scars along the bulb of the heel from apparent abscesses.
Approximately 35 stallions were in the herd. They were tough guys, excellent body condition, extremely durable, and ready to fight at the drop of a hat. Only the most dominant stallions were free of multiple war scars.
Forty-five foals were closely examined. Front and hind feet were radiographed and several foot molds were made.
No parietal groove fractures were found.
No club feet.
One foal was contracted behind with his heels well off the ground. One other foal developed severe hind limb contraction several weeks after arriving at the nursery.
The very young foals, one week to 90 days old, were relatively easy to handle, but they were very protective. They were radiographed in lateral incumbency using .2cc Dormosedan, I.V. The older foals were typical of Thoroughbred foals that get little or no handling. All were examined using Ketamine and Rompun.
What does the normal, mature foot look like and what can it tell us? Studying approximately 1,800 head, many very closely, one would like to think this would be representative of the natural foot. The range of norm was much larger than I expected to find. What influence do genetics and environment play with these feet? Does natural selection eliminate the club feet, varus deformities and other angular problems often seen with domestic horses? If so, how does this work? Are the weak and crippled culled by coyotes and mountain lions or simply starve? We do not know at this time.
One stallion, approximately 20 years old, that was gathered in the mountains north of Vegas presented with front feet that are miles off the scale from what we consider balanced. However, he led the herd as the helicopter pushed them several miles to the trap. Sound and full of himself, exhibiting only a few battle scars, he was apparently a dominant sire for his herd of mares. Apparently this was a congenital deformity, so why wasn’t it self-limiting? Why wasn’t it seen in any other horses? Were the offspring victims of natural selection? Observations by Dr. Tom Hartgrove:
1. A three to four year old mare gathered a few years ago presented with a rye mouth. The mandible (lower jaw) was 90 degrees to the maxilla (top jaw). She apparently learned to eat foliage with her tongue. What foliage? They must travel miles to get a mouth full, but she survived.
2. Metacarpus and distal phalangeal fracture found on a two year old radiographed by Dr. Tom Hartgrove. How did this one survive?
Dr. Hartgrove has examined foals, weanlings and yearlings with severe angular deformities and flexor contraction that have survived the funnel of natural selection in spite of their afflictions.
3. An aged stallion presented with a severe varus deformity of his left front pastern and foot. It took three fresh horses to catch him. He was adopted, castrated and broke to ride but became lame once he was shod with a therapeutic shoe.
What has my preliminary study taught me that I can pass to you? We have much to learn from these horses. Yes, they are as natural as one could ever expect to find and live their entire life without man’s influence. There was a relative range of “normal”, but it was quite broad. There were also very distinct characteristics and conformation unique to the gather area. All were gathered from semi mountainous, desert terrain. Yet there are individuals that fall well outside the relative normal prototype that must be considered natural as well. They defy modern day standards and are standouts in their own population but they are natural, alive, quite healthy in spite of being tested by the harshness of their environment. They are groomed by the wind and trimmed by the abrasive surface they travel on. Previous work by Dr. Hartgrove confirms they have few, if any parasites, and appear to have a foal every year in spite of being aged (20 years plus).
The typical wear pattern has a strong message. What is it? Does it mean we should make domestic feet look like the wild foot? I don’t think so. To do so would be disastrous. The domestic horse cannot survive with this length hoof capsule, and the majority of domestic soles are not genetically capable of ever being as tough as the wild horse soles given the same anatomical thickness. Apparently the environment plays a major role with the typical wild foot image, but genetics must also be a strong influence.
I cannot help but ask, “Where did the club foot go?” I have looked at approximately 1,800 wild horses and not found one club foot that falls into the 1 through 4 grading scale I use for the domestic horse. The Bureau of Land Management at Palomino Valley reported seeing several club feet from a particular herd but agreed they are quite rare. We cannot look at 1,800 Thoroughbred, Arab or other light breed horses and say the same. The absence of varus deformities is also very interesting. Being a full time podiatrist for twenty plus years I have seen a steady rise in varus deformities among Thoroughbred foals worldwide over the past ten to fifteen years. This increase appears to inversely proportional to the ever growing knowledge bank concerning herd health. The more we learn about nutrition the faster they grow and the angular problems abound. Are we doing too good a job raising foals, are we overriding Mother Nature’s plan? I think possibly so.
One of my adopted fillies, now a two year old, showed no signs of being toed-in (varus) until I started feeding her. Now she has changed her entire front limb stance. One thing is for certain, they are genetically designed to survive without the influence of man, and they do so with fewer problems. Knowing this assures me that we can learn from them and do a better job.
I have asked, “How can a multimillion dollar race horse or sport horse live under immaculate conditions, in straw up to their bellies, with a full time attendant, veterinarian, and farrier, and still have a bruised foot on the day they need to beat the world?” I feel the answer is simple. Many of these horses’ feet have lost their natural ability to heal. As farriers and veterinarians, we can only eliminate the handicaps that prevent or delay the natural healing response. We cannot make them heal. Tissue heals and repairs at a programmed rate. I don’t think we can increase this rate; I think we can only reduce it. The self-healing protocol is enhance by the natural wear pattern.
Using the four-point concept as a tool to eliminate known handicaps that delay healing has been a serious step forward for me. My version of the four-point concept leaves a foot with similar anatomical characteristics but with striking contrasts, too. We must be careful when comparing the domestic foot to the wild horse’s foot, as they are quite different in many ways.
The gross anatomy, circulation, size and shape of PIII, location of PIII within the capsule and soft tissue parameters all vary greatly from those found with domestic breeds. My unique version of the four-point trim is not designed to make the domestic foot look like those described in this paper, it is merely a tool that helps us enhance the healing mode of the foot.
The wild horse foot is a great study model but develops and matures under the beat of a different drummer. We must never forget that, and we must be careful extrapolating information from the natural occurring foot to the domestic foot. We also must remember that routine problems seen in domestic feet seldom are seen with the feral horse. At this time we do not have an accurate tracking system for the feral horse and do not know how many fall through the cracks. The stimulating message is that we can do a better job preventing common foot problems and aid recovery by simply enhancing the healing environment. Our best bred horses have poor quality feet only because we have not eliminated the handicaps suppressing natural healing.
I adopted three yearlings that arrived in Kentucky in April. All were radiographed, venograms were performed and foot molds taken in Reno. A series of photographs described the growth and break up pattern of the two fillies and one colt. The colt had odd valgus deformities in both rear feet, and the medial walls were well under the normal load zones. Once the feet grew quite long, the condition corrected itself. The light boned black filly’s feet broke back weeks before the white foot of the roan filly and remains quite uniform and well shaped months later. The colt grew very long toes and broke back quite slowly months after the fillies. The front feet remained well shaped and relatively short, while the rear feet grew quite long toes and broke back at a longer length. Wear is very important. These yearlings lived in relatively dry conditions in Kentucky this summer, but their activity in three acre paddocks does not produce enough wear. The wild horses I have observed will travel many miles twice a day for water or food, which creates a very efficient self wear program.
What is to be learned? We have just touched the tip of the iceberg. Are these tough, well shaped feet a reflection of environment or genetics or a combination of both? When does the young horse develop the double thick wall? Apparently it can revert back to a thin wall once domesticated. I examined two aged geldings that had been adopted for five to seven years. They had big strong feet but 15/15 mm horn-lamellar zones. My three cases will hopefully help us better understand this phenomenon. If the thicker wall develops, can it pass to offspring when bred to poor footed domestic horses? I hope to learn this.
What is the major energy sink or pump of the foot? I think it is safe to say it is not the frog as we have been taught (ref. Dr. Robert Bowker). The lateral or ungual cartilage may play a major role, but it is my hypothesis that it is the laminae and sole corium that moves large volumes of blood, via action of the deep flexor tendon. With every step, heat and energy that would ultimately destroy the integrity of all feet is dissipated. Studying the effects of the deep flexor with various pathological as well as apparently normal feet I hypothesize that the secret of equilibrium rests in the function of the tendon. Further research is needed concerning the complex function of the flexor sling that ultimately controls the health of the foot.