A horse with progressively whitening hairs is commonly called a “gray horse.” This designation refers specifically to a coat color and not to a particular breed of horse. Many different horse breeds can exhibit the gray coat. The visual appeal of gray horses, from deep charcoal to nearly pure white, often leads to fascination and sometimes misconceptions about their true color.
Understanding the Gray Color
The term “gray” in horses describes a unique coat color where the horse’s hair gradually loses its pigment over time. Gray horses are typically born with a darker base color, such as black, bay, or chestnut, and then progressively lighten as they age. This process means a gray horse’s appearance can change significantly throughout its life.
Gray horses differ from white horses. Gray horses possess dark skin and dark eyes, even when their coat appears entirely white. True white horses are born white and typically have pink skin and sometimes blue eyes.
Gray horses are also distinct from roans. Roan horses have white hairs intermixed with their base coat, but this pattern does not change or lighten with age. Their heads and legs usually remain darker, unlike gray horses whose heads often gray first.
How Gray Horses Develop Their Distinctive Coat
The gray coat color results from a dominant gene, the G locus (STX17), which causes progressive depigmentation of the hair. Foals carrying this gene are born with a solid, non-gray color. White hairs typically begin to appear around the muzzle, eyes, and flanks shortly after birth or by one year of age. This graying process continues gradually over several years, with white hairs replacing the original colored hairs.
Researchers have identified that a duplication in a specific DNA sequence within the gray gene influences the rate of graying. Horses with more copies of this duplicated sequence tend to gray faster and may become entirely white earlier in life, while others gray more slowly. The gray gene is a dominant trait, meaning a horse needs only one copy of the allele to develop a gray coat.
Different Shades and Patterns of Gray
The graying process manifests in a wide array of shades and patterns, representing stages in a horse’s life or variations in gene expression. These descriptions are terms used to describe the evolving appearance of a gray horse throughout its life.
- Dapple Gray: This pattern features darker rings on a lighter gray background, often seen in younger adult horses. These dapples are temporary and fade as the horse lightens.
- Flea-Bitten Gray: Small flecks of darker, pigmented hair appear on an otherwise light or white coat. These speckles, often the color of the horse’s original coat, can increase in density as the horse ages.
- Steel Gray: Also known as iron gray, this describes a darker, often bluish-gray appearance. It is typically found in younger gray horses born with a black or dark bay base coat.
- Rose Gray: This refers to a reddish-tinged gray, which occurs when a gray horse born chestnut or bay begins to show white hairs, creating a pinkish or golden hue during an intermediate stage.
- Light Gray or White Gray: As depigmentation progresses, many gray horses eventually reach this stage, where their coat becomes almost entirely white.