Sooty is complex, it is not genetically studied and little is known about it, therefore when we say ‘the Sooty gene’ that is used as a very loose term. Unlike, for example, a Grey horse, where you can track it up generations for a hundred years, it is impossible to do this with a Sooty horse as it appears in different forms on different horses and on different colours. The Sooty gene is represented in several different ways visually; in fact, it seems that there may be several Sooty genes at work, or at least that’s one theory among some people. Which makes recording it in the breeding records a difficult thing, especially with such little knowledge they had about horse colours as little as 20 years ago let alone 100!
To over simplify things Sooty, or called Smutty, is when there is a presence of black hairs when there otherwise shouldn’t be. Sooty effects are different on different horses and/or different colours. Often on black based horses the Sooty gene creates a counter shading effect, this is where the horse’s coat is darker at the top and lighten down the flanks and lightest under the belly (not to be confused with the Pangare effect which lightens the horse from the bottom of the belly getting darker around the flanks and darkest at the top line). Sometimes these horses are mistaken for a Dun horse as the dark hairs from the Sooty gene create a false dorsal stripe along the spine. A black based Sooty horse with counter shading will have one general sign showing that it is the sooty gene causing this effect; look at the horse’s neck, you will see that usually the jugular grove on the neck is lighter then the dark sooty neck around it. These black based Sooty horses with counter shading can be seen with or with out dappling. Red based horses carrying the Sooty gene often show an overall even dark coat rather then counter shading. The horses will often have what is called Bend Or Spots. When the Sooty gene and Cream gene are combined the result is usually bold and extreme dappling. Bend Or spots can be easier to see on lighter horses such as Sooty Palominos. Some horses are so Sooty that they are very dark for a horse with the Cream gene.
Sooty has not been genetically studied however there are several theories to what is at work. One theory is that there are two Sooty genes; one that works on black based horses and the second that works on red based horses. Some view the Sooty gene being a single simple dominant gene. Another theory is that there is no true sooty black based horse, and rather the horses classed as Sooty Bay and Sooty Buckskin, etc, are really just Seal Browns and Brown Creams. A theory is that Sooty red based horses are Sooty due to their Agouti status.
Check out the album to see Sooty horses: