Horse conformation is sometimes described as a complex or polygenic trait. This means that it is affected by both many genes and the environment. It affects the looks of a horse - the shape and proportions of its body. More importantly though, the movement and physiological functioning is also influenced by conformation - thus affecting the potential for performance and good health.
In reality horse conformation is the combination of many traits (characters), each influenced by different genes and also affected by the environment, especially during development.
Defects of horse conformation are also influenced by genes. They can also result from, or be exacerbated by, poor (including incorrect) nutrition or other environmental conditions (such as oxygen deprivation in the womb), especially during development, both before and after birth.
The "prefect" horse conformation is somewhat subjective, and depends on the breed, and the use to which a horse is to be put. Some features of horse conformation though are essential for the proper function and well being of a horse.
The article below describes some aspects of horse conformation, giving us guidance on what to look for in our horses. Breeders in particular should remember that, since good horse conformation has a large heritable component, they should strive to choose breeding stock that already exhibit good characteristics.
What is Good Conformation?
by Ron Petracek
Conformation—the way a horse is put together—will determine not only how sound a horse remains throughout his life, but will also determine to what extent he will excel at his particular discipline. While some points of conformation vary with the type of horse and what job he is doing, there are some general rules of conformation that most horsemen agree on.
Feet should be large enough to support the horse and his weight, and the hoof wall should be hard but not brittle. The front feet and the back feet should appear to be symmetrical from all angles. The sole should be slightly concave, and heels should be even where they join the sole.
Legs should be straight. Legs that are out of alignment can result in soundness problems, as the forces that travel up the leg of the horse as he moves will affect other parts of the body, depending upon where legs deviate. Legs should also be symmetrical, with no bumps or bulges. Each pair of legs should also match each other.
Good joints are imperative to any horse who performs. Joints should have the correct axis, and they should be symmetrical, free of lumps, cool to the touch, and should be in proportion to the size of the horse. If one joint seems too large it should be examined for injury. If all joints seem too large the horse should be examined by a veterinarian for nutritional or metabolic problems. From the front view, a line dropped from the point of the shoulder to the ground should bisect the knee, fetlock, and hoof. From the side view, the line from the front of the fetlock, along the top of the pastern, and continuing along the front of the foot to the ground should be straight.
Good shoulder conformation will depend upon what the horse is being used for, as shoulder slope and how long the shoulder is varies with breed type and use. As a general rule of thumb, horses used for speed should have a long, sloping shoulder, while those used for power have more upright shoulders.
Since withers are what keeps a well in place, any ridden horse needs to have appropriate withers. Horses with flat withers, often called mutton withers, often have difficulty being ridden up and down hills, but can sometimes fare well on the flat. Poorly conformed withers can cause pain in the ridden horse and can lead to unsoundness.
The angle and length of the hip should match the angle and hip of the shoulder. While short hip lengths rarely cause unsoundness they can negatively impact speed and power.
Back and Neck
The long back versus short back debate continues depending upon the use of the horse. While long-backed horses do tire more easily, they can be more comfortable to ride. Long-backed horses can also excel at jumping because of the scope the long back allows them. Long backs also allow more movement in the horse's legs, which is why many long-backed horses excel at driving.
The length, shape, and way a horse's neck connects to the chest and the back will vary depending upon the breed and use of the horse. Horses who run need longer necks, while horses who show in park or pleasure classes often benefit from aesthetically pleasing upright necks.
Horses need big, well-placed eyes. Horses with small eyes may suffer from impaired vision or have a medical problem. Eyes should not be set too far toward the sides of the head, otherwise peculiar fields of vision are sure to be an issue.
The nostrils should be open and symmetrical, to allow for maximum air intake. Horses with extremely dished heads or thick necks sometimes have difficulty taking in the right amount of air despite nostril size, so make sure you take these things into consideration.