All the grey horses

Grey thoroughbreds share a founding father

By Helen Briggs BBC News Online science reporter

It is well known in racing circles that all grey thoroughbreds can be traced back to one stallion, Alcock's Arabian, born in 1700.

British scientists have used the time-honoured pedigree to carry out some genetic detective work.

Using DNA samples from a stallion called Paris Match, and his many offspring, they have found the location of the gene that gives all grey horses their distinctive coat.

All the grey horses you see on the race course have a piece of DNA that descends from that original founder in 1720

Dr Matthew Binns

The discovery is part of a project to map the horse genome at the Animal Health Trust in Suffolk, UK.

As well as giving a clue to what makes a great racing horse, it could help explain why a type of skin tumour, or melanoma, is common in grey horses.

Dr Matthew Binns, head of genetics at the trust, says they wanted to test the validity of their genetic map using a physical trait that is easy to score.

Tumour link

About 3% of thoroughbred horses are grey. They are usually born black, chestnut or brown but soon become dappled, grey or white.

"By taking our genetic map and mapping the markers on DNA collected from a large number of progeny from a grey stallion we were able to map where the grey locus (the position of a particular gene on a chromosome) was on the horse genome - and found it's on horse chromosome 25 in a particular place," explains Dr Binns.

Foals enjoying the sunshine (Photo courtesy of Animal Health Trust)

Grey horses are more prone to melanomas than other horses. After the age of 10 nearly all grey horses develop the tumours, possibly because of a biochemical link between the development of their coat colour and the disease.

In collaboration with a Swedish group, Dr Binn's team plans to narrow down the search for the gene in the hope that it will give some clues to the cause of melanoma.

"If we can actually understand the process maybe in the future it would be possible to develop drugs which would block melanoma," he says.

Founding fathers

Thoroughbreds have their origins in the early 1700s, when a small number of Arabian stallions were brought into Britain and mated with a group of native mares.

"The grey gene was introduced we think just a single time in a horse called Alcock's Arabian in about 1720," says Dr Binns.

"So all the grey horses you see on the race course or on the gallops here at Newmarket have a piece of DNA that descends from that original founder in 1720."

As well as shedding light on the secret history of the thoroughbred, the research should improve the health of the breed and perhaps even its racing performance.

Patrick Cunningham, professor of genetics at University College, Dublin, says it might be possible to breed better racehorses.

"The primary pay-off is being able to select more effectively and improve the general health of the horse population," he says.

One way is to breed from horses with a desired genetic make-up. There is some evidence, for example, that some horses race better over long distances because they have a gene variation linked with stamina.

And, as new genetic tests become available, it would be possible to stop horses that carry undesirable genes from being used as stud mares or stallions.