What is a Healthy Hoof? (Bluegrass Laminitis Symposium)
Ask 10 people what a healthy hoof should look like and you'll likely get 10 variations of an answer. And those answers will probably consist of general statements like "proper toe angle," "enough heel," or "plenty of foot mass." But what exactly does that mean?
Richard Mansmann VMD, PhD, clinical professor and director of the North Carolina State University College of Veterinary Medicine's Equine Podiatry and Rehabiliation Service, has spent a lot of time and effort investigating foot measurements in horses to answer that question. At the Bluegrass Laminitis Symposium, held Jan. 25-28 in Louisville, Ky., he presented the results of several research projects that tried to answer that question: What are the characteristics of a healthy horse's hoof?
Preventive Radiographs (X rays)
Mansmann has long recommended that horses' front feet be radiographed annually--that includes sound horses as well as lame ones. "My goal with this is to look at it from the perspective of prevention rather than treating the kinds of (lameness) cases we've seen so far," he said.
These annual radiographs, along with horses' work histories, have provided a great deal of information to begin answering the question of what a healthy foot looks like. "The goal is to arrive on what we all might agree is a healthy horse's hoof," he said.
He described the following principles many consider to be characteristic of "good" feet, and described how closely his clients' horses compared to those principles. These included some preliminary data from 108 low- to mid-level adult working horses evaluated from 1998-2002: These horses had an average body condition score of 6.6, they were worked 4.21 days per week, and 3.06 weeks had passed since their last shoeing.
1. Front and hind feet should mirror their opposites.
Mansmann said hoof walls should be slightly straighter (more vertical) on the medial sides (insides) than the lateral sides (outsides). Of his 108 study horses, 84 (78%) had 4.9 mm or less difference in the widest part of their front feet, 20 (18.5%) had a difference of 5.0-9.9 mm, and only four (3.7%) had a discrepancy of 10-14.9 mm.
"The bottom line is that 90% of these working horses had 6 mm or less of mismatch between their feet (and they were sound and in steady work)," he summarized (so in general, the feet were pretty close to matching in width). He suggested that perhaps feet that varied by 1 cm or more might be predisposed to problems.
2. The anterior hoof wall is parallel to the anterior surface of the coffin bone (P3).
Why is this important? Because if the wall is not parallel to the bone, usually it is thicker nearer the ground than it is up by the coronary band. This can indicate instability and rotation of the coffin bone as occurs in laminitis, or it can be the typical conformation of an upright or club foot. With regular monitoring one can tell the difference.
Mansmann noted that wall thickness (often termed the horn-laminar or HL zone) was measured in two places--up high and perpendicular to the face of the coffin bone just beneath the extensor process and lower down, perpendicular to the distal or lowest tip of the coffin bone.
Eighteen horses had a lower HL zone measurement that was greater than the upper HL measurement by 1-5 mm, he reported. "This indicates that 9% of feet probably had some rotation; this makes lateral radiographs worthwhile. Diet control and early intervention in laminitic risk factor situations should be considered."
3. Sole plane angles are positive.
This describes horses with positive palmar angles, or coffin bones that are higher off the ground at the heel than at the toe. Mansmann reported that a negative palmar angle generally results in a broken-back hoof-pastern axis, and commented that horses will often assume this stance when they have heel pain or pain in the rear of the leg.
"Once it is flattened (by this stance) for several months, the digital cushion will not regenerate," he said. "We have started calling this reverse laminitis."
In his study horses, the average palmar angle was +2.35ï¿½ and the average hoof angle was 53.96ï¿½.
4. Thin soles are detrimental to soundness.
Thin soles are often said to provide reduced shock absorption, contributing thusly to pain and lameness. Mansmann said that sole padding (such as a soft pour-in pad) helps reduce abrasion and increase sole thickness, and possibly helps reduce digital cushion crushing by distributing load more evenly on the sole.
He reported an average sole depth of 13.97 mm (not counting the very minimal sole cup in most of these horses) under the tip of P3.
5. Hind feet have a greater (steeper) angle than front feet.
"We didn't look at hind foot angles in these horses, but the more we look at hind feet, the more we see significant problems (generally from heels that are too low)," Mansmann said. "We suspect that low hind heels cause upper hind limb and back problems. Look at the horse from the side and see where a line forward through the hind coronary band would hit him. If that line hits him in the belly, and if you palpate him over the croup, he will likely be sore (because that low heel puts a lot of stress on his back and upper limb). That coronary band line ideally should hit him between the front knee and elbow."
6. If a measurement changes on a horse, a decision must be made on whether that measurement is improving or deteriorating, and if it is the latter, it should be addressed.
"If we agree on common principles, then we can discuss when a horse's foot does not look healthy, and develop a plan to improve or at least monitor that change," he stated. "We need to understand when a foot is not doing well and not shrug it off. We need to write it down so when things change, we know when to celebrate and when to start sweating."
Implications for Soundness
"Many veterinarians and farriers do not see an unhealthy foot (such as one with an overly long toe and low heel) as a potentially serious pathologic problem; therefore, they make no record of any measurements or podiatry radiographs to monitor the problem," Mansmann said. "Owners usually concentrate on other conformational assets and not much on the feet. Orthopedists stop looking at a horse at about pastern level. And very little basic foot research is funded on normal or abnormal foot conformation and its relationship to the rest of the horse's orthopedic problems.
"Everybody believes 'no foot, no horse,' but the financial investment in hoof research is pretty minimal compared to other areas," he went on. "I think abnormal hoof conformation can be just as detrimental as a bone chip, tendonitis, muscle pull, laminitis, etc. If it is not diagnosed and treated in a timely manner, it can get worse to the point of total disuse and chronic pain for the life of the horse."
No Feet, No Sale
"I think all these foot measurements should be part of a prepurchase examination," Mansmann opined. "I think every farrier should market a prepurchase examination; it's very important to talk about how easy it's going to be to keep that horse's feet sound. Quite frequently, the farrier is asked to put shoes back on after a horse is radiographed during prepurchase examination, and this is a great time to involve yourself in this situation."
Breeding Bad Feet
Many people in the equine industry have commented that horse breeders often select breeding stock for speed, body conformation, muscling, agility --anything but foot conformation and quality. Mansmann discussed an informal evaluation of breed magazines that seemed to support this theory.
"A few years ago, I was looking at a photo of a Thoroughbred stakes winner on the cover of The Blood-Horse, and I was impressed (in a bad way) by his foot problems," he said. "But they had cured his foot problems later on by his 7-year-old stallion advertisement photoï¿½they stood him in grass for the photo," he said with a chuckle.
"We reviewed 1,852 stallion pictures in eight 2004 breed magazines," he reported. "In those photos, only 13% of the stallions stood on firm surfaces so you could get an idea about their feet. Thirty-nine percent stood in grass, 34% were action shots, and the rest were just head shots. In a Quarter Horse magazine, 25% of the horses appeared to have their feet airbrushed out."
The implications of this, he said, are that foot quality is not considered to be important and/or that poor hooves should be hidden, and mare owners are not demanding that hooves be seen in photos. "So mare owners need to ask about a stallion's foot conformation," he advised. "Bad feet can potentially be exercise-limiting and just as serious as other lameness causes."
"As veterinarians and farriers, we all need to educate owners about the value of proper foot conformation and the consequences of bad conformation," he concluded. "We have to look at the horse and his feet. When his measurements change over time, that is very good information to have. And having an unhealthy-looking foot can even end up as a life-threatening situation. It is a disease in itself."
About the Author
Christy West has a BS in Equine Science from the University of Kentucky, and an MS in Agricultural Journalism from the University of Wisconsin-Madison.
POLL: Horse Barn Air Quality