Pyrenean Mastiff Coat Colors & Patterns

The Pyrenean Mastiff can come in any combination of coat colors and patterns seen here. The Pyrenean Mastiff is homozygous for piebald.

Base Colors

The Pyrenean Mastiff's can come in a primary base color of sable ranging from pale blonde to a rich red color.
Black can be found in the Pyrenean Mastiff but is generally dark agouti or reverse brindle. Grey is often a Domino agouti combination that creates a badger color of blended browns, blacks and pale blondes.
Tricolor is tan point combined with the piebald. This is a naturally occurring color but an undesirable/serious fault color.
Solid white is naturally occurring but a disqualifying color. Very Pale almost white markings are usually Domino sable.

Head Markings

Acceptable head markings: At minimum, eyes and ears must be patched. Symmetrical markings on the face are ideal, but skewed markings are acceptable. A completely marked head is acceptable but not ideal. The white blaze can vary in thickness as long as it does not pass through the eyes.
Disqualifications/Mismarks: Eyes and/or ears are not patched.

Coat Patterns

Typical coat patterns
Brindle can be expressed as a sable base with black striping. Reverse Brindle can appear as a black base with sable striping. The sable striping may be minimal appearing all black.
Black masking can appear on he muzzle, ranging from just the muzzle to extending past the eyes and including the ears.
Black tipping on a sable coat is also possible and is usually expressed down the spine.
Coat patterns will only be expressed on patched areas of the body.

Breed Standard: About

Coat Color Locus in the Pyrenean Mastiff

K Locus

First we have the K Locus, in the Pyrenean Mastiff the K locus is either of the following:

Kb/ky or Kb/Kb is dominant black not allowing other color locus to show through. We have not seen this allele in genetic testing for the Pyrenean Mastiff yet.
Kbr/ky, Kbr/Kbr (shows in testing as KB/Ky) as it can't be identified yet) this is what produces brindle markings. dogs who are Kbr/Ky generally have more spread out black streaking in the coat (brindle) and dogs who are Kbr/Kbr have more black streaking (generally known as reverse brindle some may appear all black). This genotype generally masks over the A locus which is what allows color to peak through in brindle dogs or cover it entirely if heavily brindled.

Ky/Ky - this genotype defaults to expressing the A locus.

A Locus

The A locus only completely expresses when a dog is Ky/Ky.

ay/ay, ay/aw, ay/at are all Sable because sable is dominant on the A locus. ay/ay does not express black coat pigment (unless the dog has EmEm modifying the A locus) and is known as clear sable.

ay/aw and ay/at often produce varying amounts of tipped sable where there is black tipping on the sable hairs or black guard hairs that show through. The Kbr allele is what allows the A locus to "peek" through in a banded pattern.

Something in addition to the ay allele is Intensity linkage. There are several genes that impact the intensity of the color produced in sable dogs. This can cause the dogs to range from cream/blonde all the way to a deep red. Intensity of the color can only be decreased by lessening the intensity such as breeding a red sable to a blonde sable for example. Other coat color markers would just "mask" the intensity for a red sable. Genetically both blonde and red are the same coat color genetics just different levels of intensity/color saturation expression.
aw/aw and aw/at which are Agouti also known as wolf grey. In the Pyrenean Mastiff these are the dogs who have a black coat with lighter tones underneath in the under coat that show through. The hairs on the agouti coat are banded and because of this it often makes them appear as if they are changing colors as they grow. Agouti dogs often have a lighter crown around the ears that blends into the black coat. In brindle agouti dogs they can also appear all black.

at/at which is Tan point. This isn't a common coat color or trait in the Pyrenean Mastiff but is still possible genetically as we have seen several tan point carriers, however the dog must be ay/ay, Ky/Ky, Kbr/Kbr, Kbr/Ky to properly express it and it can be modified with the kbr allele giving brindle points.

E Locus

The E locus is a masking locus and creates an overlay over the base coat.

Em/E, Em/Em, Em/e and Em/Ea are what produce the black mask over the muzzle of a Pyrenean mastiff. This black mask over the muzzle (where there is no white blaze) can be from the nose up to past the eyes and include the ears in the Pyrenean Mastiff.

E/E, E/e, and E/Ea which is no expression and leaves colors to the other color Locus and alleles. There is no impact to the coat color.
e/e which is recessive red, this isn't very common in the Pyrenean Mastiff but like the at tan point allele we have seen it show up on genetic testing and so it is possible. e/e is what makes all Golden retrievers range from cream to deep red, the breed is homozygous for recessive red (kind of like how the Pyrenean Mastiff is homozygous for piebald). recessive red also has linkage like sable to intensity and the intensity linkage is what causes there to be a range to the expression of the color. Recessive red masks over any and all other colors and patterns (aside from the piebald where white is expressed).

Ea/Ea or Ea/e known as Domino. We are seeing this actively as dogs have been tested recently since it is a new test item.

Dogs who are Agouti aw/aw, aw/at and are also Ea/Ea or Ea/e are dogs who express the grey or badger color patches. Ea is responsible for a particular phenotype with reduced eumelanin (black) production and increased pheomelanin (yellow) expression. Domino can fade brindle striping or fade the black of agouti dogs (making it appear grey). Domino is a reduced-function mutation that can be described as partial recessive red. While true recessive red inhibits all eumelanin production, domino only reduces the amount of eumelanin in a given pattern. Domino often also turns a dog’s whiskers, hair roots and undercoat white! This is why dogs who are considered grey/badger in the Pyrenean Mastiff have blended black//grey/ and pale blondes/creams mixed in giving that color perspective. It is a muted modified version of agouti.

Now dogs who are Sable ay/* and are also Ea/Ea or Ea/e are dogs who will be prone to fading. Remember Domino also acts as a reduced-function mutation and in the Pyrenean Mastiff we are seeing that it is linked to dogs who may be born with light patches who ultimately fade to almost undistinguished from the white undercoat, faint or barely there markings. Again here Domino is acting as a muted/modified version of sable and is progressive in nature as a dog ages.

We are seeing linkage of Domino to mismarked dogs as well i.e. missing pigment on eyes and ears though there may also be other genetic coat color factors that also play into this that are not yet identified.