Mick & David Easterby

The Godolphin Arabian

National Racehorse Week: What is a Thoroughbred?

Feature | Racehorses

It's National Racehorse Week.

A week to celebrate the Thoroughbred.

But how many of those watching racing have stopped to consider what is a Thoroughbred and how they came to be?

Flat racing can be traced back in England to the twelfth century. Four-mile races took place at Smithfield, in London, but this was a long time before the concept of the thoroughbred existed.

So what are Thoroughbreds and where did they come from?

A Thoroughbred is a breed of horse developed for racing. Thoroughbreds are considered "hot-blooded" horses that are known for their agility, speed, and spirit.

The Thoroughbred was developed in 17th- and 18th-century England, when native mares were crossbred with imported stallions of Arabian, Barb, and Turkoman breeding.

The Byerley Turk

The foundation stallions

All modern Thoroughbreds trace back to three foundation stallions imported into England from the Middle East in the late 17th and early 18th centuries. The three horses were the Byerley Turk (1680s), the Darley Arabian (1704), and the Godolphin Arabian (1729).

The three stallions were bred to a larger number of foundation mares. Most of these had English breeding.

Thoroughbred pedigrees show that most horses have more crosses to the Godolphin Arabian (13.8%) than to the Darley Arabian (6.5%) when all lines of descent are considered.

The majority of modern Thoroughbreds alive today trace to a total of only 27 or 28 stallions from the 18th and 19th centuries.

The foundation mares

Mares used as foundation stock came from many different breeds. The Irish Hobby developed in northern Europe prior to the 13th century whilst other mares came from oriental breeding, including Barb, Turk and other bloodlines

However, research shows that the number of Eastern mares imported into England during the 100 years after 1660 was small.

Recent studies of the mitochondrial DNA of Thoroughbred mares shows that some of the mare lines may actually have had a common ancestor. Studies trace back to only 15 unique foundation mares, suggesting common ancestors for foundation mares thought to be unrelated.

The Darley Arabian

The 18th and 19th centuries

The 18th and 19th centuries saw the Thoroughbred breed spread throughout the world. In 1730 the first Throroughbred was imported into the USA. Then followed Australia, mainland Europe, Japan and South America during the 19th century.

How many Thoroughbreds are there?

Millions of Thoroughbreds exist worldwide today. Each year somewhere in the region of 100,000 foals are registered worldwide.

How big are Thoroughbreds?

Thoroughbreds typically range from 15.2 to 17 hands (157 to 173 cm) high. The average size is 16 hands (163 cm).

What colour are Thoroughbreds?

The most common colour is bay, whilst dark bay or brown, chestnut, grey and less frequently black are also seen.

How fast is a Thoroughbred?

The fastest speed ever recorded for a Thoroughbred is 43.97 miles per hour.

The World record holder is Winning Brew who, on the 14th May 2008 at the Penn National Race Course in Pennsylvania in the USA, covered quarter of a mile (402 metres) in 20.57 seconds. At the time she was just two years old.

However, the average equine gallop is around 27 mph.