Color genetics in Fjords
The Base Colours and Modifiers
As you will notice, the five accepted colours all include the dun factor, or more specifically, the line-backed dun factor, meaning all carry the genetics of the dorsal stripe and dark points. Since these genetic traits appear to be completely consistent within the breed, they form a basis, or canvas for all the colours of the Fjord Horse.
Though not completely consistent but nearly so, the breed also exhibits what is known as the “pangare” effect. This represents the creamy, mealy colouration around the muzzle, fetlocks, tips of ears and underbellies. Occasionally Fjord Horses apparently lacking this color trait are seen and such individuals exhibit a dark colouration around the muzzle, tips of ears, etc. with none of the normal mealy/creaminess. Some even exhibit a dirty colouration to the normally white sides of the mane. While this has met greater acceptance in other countries, such colour expression has been selected against both institutionally and among breeders in Norway for the better part of a century.
Brown Dun (brunblakk)
In the Norwegian Fjord Horse, the brown dun colour functions as a dominant genetic factor, just as brown eyes do in people. In the absence of any other genetic modifiers, a Norwegian Fjord will always appear as a brown dun. The base color in the absence of the dun factor would be bay. Brown dun Fjord Horses can range from very light brown to very dark brown. Approximately 90% of all Fjord Horses are this colour.
Grey Dun (grå) and Red Dun (rødblakk)
The genetics responsible for both grey and red dun Fjord Horses are inherited recessively. This means the genes responsible must come from both sire and dam and also that the parents can be carriers without exhibiting the colour (expression) if they only carry one copy of the gene. A parent that exhibits the colour will always pass one copy of the gene responsible for expression to its offspring. A parent that does not exhibit the colour, but is a carrier of the recessive gene has a 50% chance, with each mating, of passing its copy of the gene responsible for expression.
Functionally, the genetics responsible for grey dun Fjords remove the limitations of the black to just the dorsal stripe and points, allowing the black hairs to run throughout the coat. This is genetically the same as grulla, not grey as it is used in standard equine terminology. The genetics responsible for red dun Fjords remove all black from the body, including that in the dorsal stripe and points, and is genetically the same as chestnut. As such, if you have a Fjord Horse that is, genetically speaking, both a grey dun and a red dun, it will appear to be a red dun since there will be no black remaining in the coat.
Just as there is a range from lighter to darker in brown duns, grey duns can range from “light silver to a dark slate” and red duns can range from blonde with a nearly indistinguishable dorsal stripe to a more brown coat with a distinctly reddish dorsal stripe.
Grey dun and red dun Fjord Horses represent approximately 4% and 3% of the breed, respectively.
White Dun (Ulsblakk), Yellow Dun (Gulblakk) and “Kvit”
The gene responsible for the white dun is commonly referred to as the “creme” and functions as a dilution gene. It is passed on directly from parent to foal. This means that without expression in the previous generation, it is impossible for a foal to have it in the subsequent generation. In one dose, the creme gene results in a white dun if the underlying genetics are that of a brown dun, a yellow dun if the underlying genetics are that of a red dun, and a lighter coloured grey dun if the underlying genetics are that of a grey dun. Because the grey allows for the black hairs to run throughout the entire coat, it is possible for this to mask the presence of the creme.
Since the gene is passed directly, a white or yellow dun can only be produced from an unbroken chain of white, yellow or grey duns, the latter only if the resulting white or yellow dun has a white or yellow ancestor preceding an unbroken chain of greys.
In two doses, the result is a “kvit” or pseudo-albino. This is not a true form of albinism as the underlying skin is still dark in pigmentation. This is the genetic equivalent of a perlino or a cremello if the base dun colour package of the Fjord Horse were to be removed. This genetic variation has been discouraged and is not registerable in Norway where it was noticed that these foals were “white and walleyed” and displayed some signs of photo-sensitivity. As such, matings between white duns, yellow duns, and white duns to yellow duns are discouraged as the resulting foals could end up with two doses of the creme gene.
While white duns were once the prevalent color, today white duns and yellow duns represent approximately 2.5% and less than 1% of the breed, respectively.