Horse colour

Grey

Grey is the dominant gene responsible for the gradual and progressive depigmentation (fading) of the carrying horse. Grey can not be considered a base-colour, or a dilution, rather a gene which slowly removes pigment from the coat. Grey is considered to be the 'strongest' of all coat modifiers, and acts upon any base-colour regardless of the carrying horse's phenotype.

The fading process itself may last for several years, but once hair is depigmented it will never re-develop with the horse's original colouring.

Since Grey is a dominant gene, where it is present it is expressed - however the final phenotype of the carrier will vary from horse-to-horse. Some Grey horses fade to full depigmentation (almost pure white) whereas others may be 'fleabitten' - whereby Grey has faded almost all of the horse's coat but for a few tiny spots or 'fleabites.' The grey carrying horse may also experience depigmentation of the skin itself, and before skin is fully faded may display 'mottling'.

Animal Genetics offers DNA testing for the associated gene mutations responsible for Grey. The genetic test verifies the presence of the dominant Grey Gene (designated G) and presents results as one of the following:

gg: - Negative (non Grey horse)

Gg: - Heterozygous. Positive for dominant Grey gene, carrying a single inherited copy. Carrier's coat modified and eventually depigmented.  Heterozygous grey horses are statistically likely to pass the gene to 50% of their progeny when bred.

GG: - Homozygous. Positive for dominant Grey gene, carrying two inherited copies. Carrier's coat modified and eventually depigmented. Homozygous grey horses are genetically bound to pass the gene to 100% of their progeny when bred, all foals will receive grey and fade-out.

Why test for Grey?

Genetic testing of the Grey gene may be beneficial for a number of reasons:

Breeding purposes: For those interested in specifically breeding grey foals, Homozygous grey specimens are ideal, as they will always transmit the grey gene when bred, thus guaranteeing (eventual) grey progeny. Those looking to 'breed out' the Grey modifier to gain non-fading foals, may hope for Heterozygous Grey horses. Some breed-types have a large percentage of Grey stock, which through historical lineage may harbour colours and dilutions 'hidden' by the masking effect of the grey.

Insight into potential a foal will fade: Since Grey may cause slow depigmentation, it may not be visually apparent as to whether or not a newborn foal will eventually fade to grey. The depigmentation process may take many years, and therefore DNA testing is useful in the cases whereby a foal is born of one or more grey parents and verification of the presence of Grey is necessary.