Conformation: form to function
Without acceptable conformation, there is limited function. Horses are commonly expected to perform in ways that are not natural for their form. A horse that is correct in form and for its intended use may be more comfortable to ride than a horse with poor conformation. Poor conformation in a horse may result in a greater risk of injury, difficulty in training, and greater lameness issues. Owners need to evaluate and utilize horses that possess acceptable conformation for the intended use of the horse. These evaluations will result in performance at optimum levels.
Many rules of conformation are based on geometry and physics. These are “general” rules that allow us to review a horse's athletic ability. For each athletic ability, there are unique attributes that are specific to the type of performance desired. This explains why hunters, halter horses, and reiners are all designed differently. Each performance horse is built to excel in his discipline with unique traits, such as the type and degree of muscling in a halter horse.
Many times the first thing that attracts your eye to a horse is their head and neck. A head and neck that are well proportioned not only gives a pleasing aesthetic appearance, but provides for a balance point that allows for effective communication via the bridle and rider. A general rule is that a horse's neck length should be one and a half lengths of their head. Head length is measured from the front of the muzzle to the top of the poll. That measurement times 1.5 should equal the distance from the poll to the middle of the shoulder. Having these attributes provides a balanced head and neck combination. A horse with too large of a head will travel very heavy on the front end and have a tendency to be clumsy. A horse with too small of a head will lack counterbalance and may lose some its suppleness and action in its front end. When evaluating the details of the horse's head, look for bright, bold, wide set eyes, ears that set slightly below the poll, a lower jaw that is clearly defined and well separated underneath the jaw, nostrils should be large, and a clean throatlatch lacking heavy fat and muscling.
When reviewing the neck, look for a proportional neck and body. The geometry equation for a balanced neck and body is the length of neck equals one third of the horses total body length, and should be equal to the length of the horse's front leg. The union of the head and neck is determined by two bones called atlas and axis. These first two cervical vertebrae allow the horse to shift his balance while traveling, thus the importance of this connection. The head should be attached on the neck at an angle so that the horse can flex at the poll and travel in a balanced manner. The neck should attach to the horse's body fairly high with a distinct chest area below. The base of the neck should be level with the point of the horses shoulder. This allows the horse to be more flexible, balanced and collect more naturally.
Divide the horse into three parts; first from point of chest to just behind heart girth (chest), second from behind the heart girth to point of hip (back), and third from point of hip to point of buttock (croup).
The shape of the horse's chest is an important part of its stamina and endurance. Chest conformation also determines lung capacity. Many horses have 18 pairs of ribs, but may range from 19 to 17 with the exceptions being Thoroughbreds and Arabians. Extra ribs allow for a shorter lumbar vertebrae area which results in stronger “coupling” of the loin area. The loin is the muscle portion of the back behind the saddle, typically from the last rib, to the point of the croup.
The underline of the horse should rise gradually to the hindquarters. Horses that have “spring of rib” have ribs that project outward, have large spaces between the ribs, are shorter backed and have a strong loin. A wide chest shape is favored by most horsepersons. From the front, a wide chest allows for lung expansion, which allows for greater endurance and more room for muscle attachment. The better combination of ribs and chest, the stronger the attachment of legs, shoulders and neck with the rest of the body which creates a powerful athletic performer.
The horses back must be functional and withstand the stress of work. The back transmits the force and driving power from the hind legs. A horse should have well-formed withers that allow for attachment of the shoulder to the rest of the horses body. The length of the horses back can be measured from the middle of the withers to the point of hip. This should be one third the length of the horse. A horse's back should be longer than their underline.
A horse with a long neck and short back provides the best maneuverability of head and neck, while the short back allows strength for carrying the weight of the rider.
Towards the rear of the horses back is the croup. This is the highest point of the rump. The croup helps with the transmission of energy for thrust and power in the hind end of the horse. Croup height should not be too high, but rounded with muscle to provide a smooth contoured shape. The croup should be at the same height when compared to the withers to maintain balance in the horses overall confirmation. The quarters are positioned below the croup. When viewing the quarters, they should not be too sloped or too flat. The length of the quarter can be measured form the point of the horse's hip to point of buttock. This length should be about 1/3 of the horse's body length using the proportions as described above.
A properly formed front leg will move in straight lines and have less stress on bones, tendons, ligaments and muscle mass. Deviations or crooked front legs can produce stresses and lead to possible lameness. Conformation of the horse's front legs can affect their athletic ability, soundness, stride, speed and agility.
When a horse stands square, the angle of the shoulder blade and the horizontal line should measure between 40 and 55 degrees. One way to measure this angle is to measure down the center of the shoulder blade to the point of the shoulder, then draw a line across the body. With this angle you should notice the horse's elbow is directly below the front of the withers.
The elbow of the horse should be parallel to the horse's body and not be turned in or out. From the front of the horse, there should be a straight line from the point of the shoulder down the center of leg, bisecting the forearm, knee, cannon, fetlock joint, pastern and hoof. The cannon bone in the foreleg should be shorter than that of the rear leg. From the side of the front leg, a straight line should be formed in front of the withers to down the center of the front leg and touch at the heel.
The angle of the pastern to the toe should also be measured at 40 to 55 degrees. An adequately sloped hoof will transfer weight from the tendons to the upper leg of the horse, decreasing pressure and maintaining soundness.
Horses with straighter shoulder and pastern angles tend to have shorter strides. However, some disciplines tend to prefer horses with a shorter stride.
The hind legs tend to have fewer lameness issues compared to the front legs because the front legs carry about 60% of the horse's weight compared to 40% of the weight being carried on the hind legs. However, front vs. rear leg lameness tends to be connected to overall horse use. Hindquarter conformation influences a horse's capacity for speed, agility, propelling power, and strength to maintain and hold collection. No matter the shape of the hindquarter of the horse, there must be symmetry and balance of muscle with the rest of the body. Running, jumping and other forward movements depend primarily on the muscles of the hind quarters, thigh and gaskin.
A long hindquarter allows for an increased range of extension and flexion. However, for power and strength, a shorter hindquarter is desired (i.e. think of a Quarter Horse vs. a Warmblood). The connection from the hindquarter to the gaskin thru to the hock is one of the keys to the structure of the hind leg. A strong well placed hock will make the leg stronger and more efficient in moving. Large formed hocks are preferred. A larger joint, with more surface area for absorbing concussion, generally makes for a sounder joint.
The hock should be level with the top of the chestnut on the front leg, which is located a few inches above the knee. Viewing from behind, the hock should be directly under the point of the buttocks, but slightly pointed inward. From the rear view, an ideal hind leg should be in-line with the point of the buttock to slightly inside of the hock to the middle of the hoof.
When viewing from the side, the hock should be wide from front to back and set on top of a sturdy cannon bone. The hind cannon bone is usually longer and wider than the front cannon bone. From the side of the rear legs, a line should be dropped from the point of the buttock, to the hock, down the back of the cannon to behind the heel of the hoof.
Correct conformation, overall balance, and symmetry are exhibited in the best horses of each breed, with all body parts showing proportion. Length and proportions play a determining role in form to function.
When examining a horse for conformation, the temptation to place the center of attention on legs is important, but the horse's body proportions are important as well. A body that is balanced and proportionate plays a fundamental role in proper leg structure and attachment.
A proportionate horse is usually square. Square means the height from the withers to ground should equal the length of body, which is the distance from the point of shoulder to the point of the buttocks.
The proportionate horse will exhibited all the qualities that have been discussed to this point which are: a neck that is long and balanced tying into a long sloping shoulder, a top line that is short and strong, a desirable underline that is longer than the top line, and front legs (from elbow to fetlock) that equal the length of depth of body (from top of withers to bottom of girth).
A horse that is proportionate will also exhibit symmetry on both sides of its body. If there are faults of a horse's conformation, those faults should be symmetrical. Lack of symmetry will cause stress on those points, causing harm and obstruct the horse's ability to perform with grace and ease.