Most warmblood registries recognize breeding stock from any other registry that is a member of the World Breeding Federation for Sport Horses, which is affiliated with the IOC-recognized International Federation for Equestrian Sports.
The Trakehner is an exception, so though some other breeds are used within the breeding population, this horse is considered a true breed. The Hanoverian, Holsteiner, and Selle Francais studbooks are also considered slightly less open than others.
A defining characteristic of a Warmblood registry is studbook selection, though even some purebred breeds in Europe use this practice. Studbook selection is the use of external evaluation – critiquing conformation and movement – of potential breeding stock to cull out unsuitable breeding horses and direct the evolution towards a particular goal. Today, studbook selection usually entails a performance proof in addition to external evaluation, particularly for stallions.
Standards of conformation and movement are not designed to perpetuate a particular ancestral type, but rather to meet a particular need. This concept is illustrated by the history of the Oldenburg horse through the past 150 years: in the late 1800s, the standard called for a heavy but elegant, high-stepping carriage horse, in the early 1900s for a heavier, stronger, economical farm and artillery horse, and since 1950 for a modern sport horse.
The most critical characteristic of a Warmblood registry is that its breeding goal or “breeding aim” is to breed sport horses. Each registry has a slightly different focus, but most breed primarily for show jumping and dressage, though many include combined driving and eventing as well.
The breeding aim is reflective of the needs of the market. In eras and regions which called for cavalry mounts, Warmbloods were bred to fit that need; when and where horses for light to moderate agricultural work were needed, Warmbloods have filled those roles, too. The purposeful evolution of the standard breeding aim is another characteristic of the Warmbloods.
Warmbloods have come into their own since the end of World War II, when mechanization made agricultural horses obsolete and recreational riding became more widespread in the western world.
The ancestral types are referred to as the heavy warmbloods and are preserved through special organizations. The heavy warmbloods have found their niche as family horses and in combined driving.
Most warmbloods were developed in continental Europe. Germany is particularly known for breeding warmbloods.
The best-known German Warmbloods are the Hanoverian, Holsteiner, Oldenburg and the purebred Trakehner. Others include the Württemberger, Rhinelander, Westphalian, Zweibrücker, Brandenburger, Mecklenburger, and Bavarian Warmblood. Several of these breeds are also represented by ancestral types such as the Ostfriesen and Alt-Oldenburger, Alt-Württemberger, and Rottaler.
Western European warmbloods include the French Selle Français, Belgian Warmblood, Zangersheide, Dutch Warmblood, Swiss Warmblood, Austrian Warmblood and Danish Warmblood. Scandinavian countries also produce high-quality warmbloods like the Finnish Warmblood and Swedish Warmblood.
Warmblood registries which are not based in continental Europe include those that regulate the breeding of American Warmbloods and Irish Sport Horses.