Gray (Presence)

Description

Gray is the gene responsible for the gradual, progressive loss of pigment that turns a horse white with age. It is not a base color or a dilution — it acts on whatever color the horse was born, slowly stripping pigment from the coat. Gray is the strongest of all coat modifiers: a gray horse will eventually fade regardless of its underlying color, and once hair has lost its pigment the original coloring never returns.

Gray is caused by a 4.6-kb duplication in intron 6 of the STX17 gene. It is dominant, so a single copy produces the phenotype. The final appearance varies: some horses fade to near-white, others become flea-bitten, keeping small speckles of their original color.

What this test reports

This test reports whether a horse carries the gray mutation — present or absent. It does not report how many copies the horse has. If you need to know whether a gray horse will pass gray to every foal or only half of them, order Gray (Complete) instead, which reports zygosity.

Why test for gray

Gray masks other colors. A gray horse may carry cream, champagne, silver or pearl with nothing visible to show for it, so color-testing programs routinely include gray to make sense of the rest of the panel.

Testing is also useful in young stock. A foal born to gray parents may show no sign of graying for a year or more, and a DNA test answers at birth what otherwise takes several seasons to become obvious. It settles the question for horses whose coats are ambiguous, too — a light roan or a rabicano can be mistaken for early gray.

Possible results

Breeds Affected

Arabian, Shagya Arabian, Andalusian (PRE), Lusitano, Lipizzaner, Percheron, Camargue, Connemara, Welsh Pony, Thoroughbred, American Quarter Horse, Standardbred, Warmblood, Mustang

Reference

A cis-acting regulatory mutation causes premature hair graying and susceptibility to melanoma in the horse.

Related Tests

• Gray (Complete) — same gene, reports one copy or two
• Red/Black Factor (Extension) — the base color gray is hiding
• Agouti — determines bay versus black underneath

This test is included in the Color Panel, which covers eight color tests for $75.