The ancestry of the Thoroughbred can be traced back to three foundation sires: the Darley Arabian, the Godolphin Arabian and the Byerly Turk. These horses were named for their respective owners -- Thomas Darley, Lord Godolphin and Capt. Robert Byerly -- who brought the stallions from the Middle East to England in the 17th century. The result was the development of the Thoroughbred, a breed of horse that could carry weight at sustained speed over extended distances.
Thoroughbred racing has a colorful and storied past, having been introduced in the American colonies before the Revolutionary War. Today The Jockey Club, formed in 1894 as the breed registry for all Thorougbreds in North America, registers approximately 23,000 foals annually. It also maintains the American Stud Book, first published in 1873.
All Thoroughbreds in the Northern Hemisphere celebrate their birthday on January 1. A newborn horse is known as a foal until it is weaned from its mother generally in the fall, at which time it becomes a weanling. On the following New Year's Day, regardless of its foaling date, the young horse turns 1 and is known as a yearling. On its second birthday, it is eligible to race.
Intact males are known as colts until they turn five, after which they become horses. Females are fillies until their fifth birthday, when they become mares. The parents of a foal are the sire (father) and dam (mother). The sons and daughters of a stallion are his progeny or get, while those of the dam are her produce.
The Jockey Club oversees the naming of all Thoroughbreds in the U.S. Owners submit proposed names to The Jockey Club for approval. A number of restrictions govern the naming process. For instance, names may not be longer than 18 characters, including punctuation and spaces, and the names of certain famous horses, such as Secretariat, cannot be used again.
Thoroughbreds come in a variety of colors. Fans may be disappointed to learn that few are black. Grey and roan are also uncommon, while white is extremely rare. Nearly 90 percent of all Thoroughbreds registered with The Jockey Club are a variation of brown -- either bay or dark bay or brown. The other official colors are chestnut, black, gray, roan and white.
Here's how The Jockey Club differentiates among the less obvious colors:
Bay: The coat varies from a yellow-tan to a bright auburn, and is distinguished by a black mane, tail and legs.
Chestnut: The coat, mane, tail and legs range from a red-yellow to a golden-yellow.
Dark Bay or Brown: The coat varies from tan to dark brown, with the mane, tail and legs being black.
Gray/Roan: A gray's coat is a mix of black and white hairs, and the legs, mane and tail are black or gray. A roan is a mix of red and white hairs, with the legs, mane and tail being black, chestnut or roan.