Study reveals cause of ‘fast-greying’ in horses
Many white horses are born with a normal coat pigment, which lightens to become grey or white.
New research has suggested that gene variations could be the reason why some horses turn white as they age while others remain a ‘dappled’ grey colour.
The study, conducted by scientists from the Texas A&M College of Veterinary Medicine and Biomedical Sciences (VMBS) and Uppsala University in Sweden, suggests that the number of copies of a small DNA sequence could explain the different speeds of greying.
Horses which are born white have a gene variant that causes them to grow a white coat. However, many white horses are not born with this gene variant.
Instead, these horses are born with a normal coat pigment, like black or brown, which lightens to become grey or white. This process starts within the first week after the horse is born with their eyelashes and the hairs at the base of their tail growing grey.
The speed at which the horse turns grey appears to be related to how many copies of the duplicated DNA sequence in the grey gene that the horse has. Horses that have gene variants with two copies of the duplication tend to be ‘slow-greying’, while those with three copies will be ‘fast-greying’.
A horse that is slow-greying typically doesn’t show signs of greying until it is five to seven years old.
A horse’s grey or white coat colour does not appear to have any influence on its athletic performance or overall health.
However, a horse’s coat colour has been linked to melanomas. The skin cancer has a well-established link with horses with the grey gene.
Leif Andersson, a professor at VMBS’ department of veterinary integrative biosciences and at Uppsala University, said: "Horses that are 'fast-greying' are more likely to develop melanomas, whereas we don't see an elevated risk in horses that are 'slow-greying'."
The researchers hope that their growing understanding of coat colour and equine genetics will further research into preventing and treating melanomas in grey horses.
The full study can be found in the journal Nature Communications.
Image © Shutterstock
The BSAVA has opened submissions for the BSAVA Clinical Research Abstracts 2026.
