Conformation and Function
Whether we realize it or not, conformation--the way a horse is built--drives almost everything we do with horses. It affects our choice of horse for specific jobs, and it affects how well their bodies hold up to the stresses of those jobs. At the 2008 American Association of Equine Practitioners convention, held Dec. 6-10 in San Diego, Calif., attendees were treated to an in-depth presentation of conformation and its effects on soundness by veterinarian G. Marvin Beeman, MS, DVM, of the Littleton Large Animal Clinic in Colorado.
Beeman is renowned worldwide for his understanding of conformation, based on being a professional horseman for 69 years and a veterinarian for 51 years; he had presented this information in 14 countries at the time of this presentation.
"Conformation assessment of horses is still largely based on subjective criteria and empirical evidence," said Beeman, quoting a 2006 study. However, he noted that research into locomotion as it relates to performance and soundness will make this subjective study more objective.
Conformation isn't everything, though. "There's always a horse that shouldn't run or jump well, but does," he went on. "Other intrinsic factors (such as the will to win) make them capable of doing well, and there are other factors such as degree of training, physical fitness, health status, rider skill, and tack. And near-perfect conformation will not protect a horse from lameness if stresses on him are too extreme (such as racing in mud over dense/hard soil that is frozen).
"The key is, can a horse do the things we ask of him and remain free of unsoundness?" he asked. Under typical circumstances, good conformation will allow this.
Keys to Evaluating Conformation
The first key to evaluating conformation is to have a standard of excellence in mind for that horse's breed and intended job. "To be a student of conformation, in my opinion, you have to have that standard of excellence in your mind every time you walk up to look at a horse," he commented.
Trial by peers is one of the purest ways to establish a standard of excellence, he noted. "Racing is one of the best trials by peer," he explained. "It has the least influence by man's judged opinions, and there is the least variability in factors to be their best. Track surfaces are basically the same, and tracks are measured to the inch. They're much more similar than endurance trails, jumping courses, etc. When a horse reaches supremacy here, you have to look at him."
However, speed isn't everything, even in racing; a horse can have speed and poor conformation, which leads to a short career because poor conformation causes excessive stress on particular structures and, thereby, lameness/injury. The ideal horse for a long career is one with good conformation, speed, and heart.
A successful polo pony has conformation that allows it to negotiate tight, fast turns with a rider perched several feet above its own center of gravity.
The second key is to understand the dynamics of locomotion. "We're not just looking at horses' conformation to see what they look like; we're looking for how they can handle the dynamics of locomotion," he said. "We want to see what makes polo ponies able to handle doing tight turns with heavy rider three to four feet above their center of gravity; how a Standardbred can trot faster than many horses can run; or how an American Saddlebred has a five-speed transmission. The skeleton is the key to a horse's method of progression (way of going) and the foundation of its conformation."
The third key is to evaluate how conformation might contribute to future unsoundness. "Conformation is the common denominator of the horse's ability to perform and stay sound," he said. "For example, 60-65% of the horse's weight is borne by the front limbs. If the horse's conformation puts more weight on the front limbs, this will contribute more to future unsoundness, as the front limbs are already the site of most lamenesses.
"Conformation defects distract from the standard of excellence, limit the dynamics of equine locomotion, and predispose the horse to unsoundness," Beeman stated.
Beeman recommended dividing a conformation exam into five categories. "This keeps me from missing things I know I used to miss," he commented. The categories are as follows:
- Head, neck, body, and balance;
- Forelimb (from the top of the scapula, or shoulder blade, to the bottom of the foot);
- Hind limb (from the top of the croup to the bottom of the foot);
- Type; and
- Way of going.
"The plumb (straight vertical) line concept is very useful in understanding deviation of the limbs that is considered to be detrimental to the horse's ability to perform and remain free of unsoundness," noted Beeman. "The basic premise is that strain and concussion will be concentrated where there is a change of direction in the plumb line stress (wherever the horse's conformation deviates from the plumb line)."
Head, neck, body, and balance Beeman listed the following ideal traits:
- Head length should be just long enough to provide room for the teeth and a nasal passage long enough to facilitate the functions of the turbinates, which temper the temperature of the air going to the lungs and trap debris that is inhaled into the nostrils when the horse is breathing hard. A bigger head just adds more weight to the end of the neck and compromises balance.
- Large nostrils allow maximal air intake.
- Large eyes placed at the edge of the forehead enhance the field of vision.
- A clean throatlatch area with a wide lower jaw provides plenty of space for air, food, blood, and nerves to pass through without interference.
- A long neck lets the horse move the head to adjust his balance and reduce weight on the forelimbs.
- For riding horses, strong withers help keep the saddle off the scapula and in the middle of the back without excessive girth pressure. "Or you have to cinch them so tight their eyes bug out," he said with a smile.
- The back should be straight and flat to support the rider's weight and that of the horse's body.
- The croup should be long, whether it slopes or not.
Forelimb A plumb line dropped from the tuber of spine of the scapula (an enlargement of the spine roughly in the middle of the shoulder blade) should bisect the column of the limb down through the fetlock and fall just behind the heel (when viewed from the side), he said. From the front, a plumb line from the center of the shoulder should bisect the limb evenly, including the foot. Additional desirable characteristics are as follows:
- The knee should be large, facing squarely forward, and placed in the center of the limb when viewed from the front.
- The cannon bone should be considerably shorter than the radius (bone just above the knee) to make it easier for the horse to pick up and move his foot (less leverage required). It should also be thick enough to withstand the forces on it without failing.
- The humerus (bone above the elbow) should be long enough to place the elbow as close as possible to a plumb line dropped from the horse's center of gravity to the ground.
- The shoulder should be long enough to enable a free striding motion, and the shoulders should be placed on the horse's side (not at the front corners of his body, which can result in paddling out as the shoulders move around the corner of the body).
Proper lower limb conformation (both for front and hind feet) is also essential. "In the author's experience, uneven feet (especially front feet) are an issue of consequence in that more than 60% of the lameness encountered in the foot will be in the one that has a smaller frog, more vertical bars, enlarged heels above the coronet band, and a greater distance from the bearing surface of the heel to the coronet band," noted Beeman. He offered the following desirable hoof conformation traits:
- The angles of the hoof wall at the toe and the pastern should be parallel.
- Pasterns should be neither too long and sloping (which hyperextends the fetlock and overstresses the suspensory apparatus), nor too short and upright (which increases concussion on the fetlock, lower phalanx bones, and the foot). "The angle of the foot and pastern has a physical effect on the angle of the fetlock, which is the major site of the change of direction and absorption of the force being directed down the limb," he explained. "The fetlock should be large enough to handle the stresses of changing the direction of forces from the upper limb to the foot."
- The pastern angle should not be broken back or forward.
Hind limb A plumb line from the point of the horse's buttocks should ideally touch the point of the hock and run along the cannon bone, falling just behind the heel at the ground. From the rear, the plumb line from the point of the buttock should evenly bisect the entire limb and hoof.
"The hock is the most common site of hind limb lameness, but the stifle is becoming more and more of an issue because of the straighter hind limb in many of the larger breeds," he noted. Conformational issues in the hind limbs are "more tolerable" than in forelimbs because there is less weight on them.
Type "Horses designed for speed and horses designed for draft work have tremendous differences in their form and functions," said Beeman. "Consider how horses are structured to do their jobs--think of the mass of the hind-end anchor for a cutting horse, for example. Different types of horses have characteristics that fit them for certain uses. You're not going to outrun a Thoroughbred with a Quarter Horse for a mile and a quarter. You're not going to outrun an Arabian in a hundred-mile race with few, if any, other types of horses. And you're not going to rope a bull with Arabian; you need a heavier Quarter Horse or you'll get dragged off into a creek. It doesn't matter what type a horse is though, his conformation is still very fundamental to his ability to do his job."
Way of going "The flight of a horse's lower limb as dictated by his conformation is best assessed at a walk, because only one limb is moving at a time (four-beat gait) and the speed is such that it can be observed easily," said Beeman.
"Understanding the conformation of the horse not only will add to the veterinarian's ability to manage lameness, it will assist him in dealing with his clientele on horseshoeing issues, purchase examinations, and selection of breeding animals," he commented. "Conformation is the deciding factor as to whether or not an individual may be used (successfully) for a specific function."
In conclusion, he quoted author W.J. Miles as saying, "â€…'Whoe'er expects a perfect 'horse' to see, expects what never was, or is, or e'er shall be.'"
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: Radiographs for Hoof Care