Sooty (gene)

Sooty is a term used to describe certain shades of horse coat color. Horses with the sooty trait have black or darker hairs mixed into their coats, typically concentrated along the top of the horse and less prevalent on the underparts. The precise genetic mechanism, or series of mechanisms, is not well-understood but the trait is presumed to be heritable.

In most cases, sooty coats exhibit pronounced countershading; the dorsal region is darker than the ventral region. However, some forms seem to produce darker lower parts. The "false dorsal" or "countershading dorsal" can mimic the dorsal stripe associated with dun horses and is associated with the sooty trait. The most extensive expression of sooty produces a dark, often-dappled cast oriented down from the topline. Many horses with the sooty trait have a darker mask on the bony parts of the face.

It was once thought that the sooty trait was responsible for turning chestnut into liver chestnut,cite web |url=http://members.aol.com/mfthorses/sponenbg.htm |title=Horse Color Genetics |author=Dan Phillip Sponenberg] however it is not known to evenly darken the coat.cite web |url=http://www.equinecolor.com/modifiers.html |title=Modifiers |work=Equine Color |date=2003 |accessdate=2008-03-05] The sooty trait is responsible for many dark bays and has a particularly pronounced effect on buckskins and palominos.

Horses without any sooty effect are termed "clear-coated."

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