In Labrador Retrievers, both yellow Labs and black Labs should have black pigment and chocolate Labs should have brown. The most common places where pigmentation is visible are the nose, lips, gums, feet, tails, and the rims of the eyes. Pigment can appear black, brown, light yellow-brown, flesh colored, pink or “liver”. The American Kennel Club breed standard states, “Nose color fading to a lighter shade is not a fault. A thoroughly pink nose or one lacking in any pigment is a disqualification.”
We, at Trinity Labradors, have worked very hard to understand color genetics in order to breed Labradors with correct pigment. Because most pigmentation effects appear in regard to yellow Labs, and sometimes chocolates, the majority of this article covers pigmentation with the yellow Labrador. So, let’s take a look at the genetic factors that determine pigment and some of the conditions that contributes to fading.
Though many breeders use this term to describe a dog born without correct pigment, the term Dudley nose is used to describe a nose lacking black pigment and is lighter than it should be.
A dog’s pigmentation is determined by multiple genes and it is possible for recessive genes to emerge many generations later. The pigmentation of Labradors is controlled by melanin, a pigment molecule. Melanin is controlled by the “B” locus and when its gene product is made, it is packaged into melanosomes, small organelles in each cell. Melanosomes are transferred by melanocytes into the cells that make up the structure for the eyes, hair, and skin. The color of the cells is determined by the color of the melanosome and the density of melanosomes within the cell. There are two types of melanin; Eumelanin and Pheomelanin. Eumelanin is responsible for black or brown pigment and Pheomelanin is responsible for red or yellow pigment.
Eumelanin, controlled by the B locus, is responsible for producing and packaging the melanin into the melanosome. Both the “B” and “b” alleles will produce eumelanin that contribute to pigmentation, but the dominant allele “B” is more efficient and packs more melanin into each melanosome, producing a black dog. The less efficient recessive allele “b” is responsible for chocolate coloration when the individual is homozygous recessive at the B locus.
For the purposes of illustration we will say that B=Black and b=brown. Each parent provides the offspring with either a “B” gene or a “b” gene. Black is dominant over brown. This means if either gene from the parent is “B,” the offspring’s genetic code for coat color will be Black. The genetic combinations include:
• BB = both parents provide a Black gene
• Bb = mother supplies Black, father supplies brown; or mother supplies brown, father supplies Black
• bb = both parents provide a brown gene
An offspring with one or two “B’s” will have a Black nose; one with two “b’s” would have a brown nose.
Breeding in order to correct pigmentation often lacks dependability. Because color is determined by many genes, some of which are recessive, crossbreeding a pigmentation non-standard yellow Lab to a black Lab may not correct the matter or prevent future generations carrying the same recessive genes. For similar reasons, crossbreeding chocolate to yellow is also often avoided. Fortunately, DNA color testing can be performed, which is available for around $85. This is the best way to determine the genetic combination of a dog for breeding purposes.
Factors that Can Result in Nose Fading
There are several problems that can occur with nasal pigmentation in Labradors that result in loss of pigmentation (i.e. nose fading). While a dog with a completely pink nose should be disqualified from the show ring, dogs with originally black noses that fade are acceptable. Some Nasal Pigmentation problems that result in fading include:
It is very common for a yellow Labrador that has black pigment to gradually turn pink with age. This is due to a reduction in the enzyme tyrosinase, which indirectly controls the production of melanin. Tyrosinase is less produced with increasing age (beginning around two years of age). As a result, the nose color of most yellow Labradors will gradually fade (and eventually turn a shade of pink) as they grow older.
2. “Winter” or “Snow” Nose
One of most common causes of a fading nose is called “snow nose” or “winter nose,” which is when the dog’s nose fades during the winter months and returns to black with the warmer months. The cause is a breakdown of tyrosinase, which is responsible for producing pigment. Tyrosinase is temperature sensitive. It works more effectively in warmer temperatures, which explains the fading of the nose during winter months or in areas where the climate is cold. It should be noted that with a true “winter nose” the nose will turn black with warm temperatures.
3. Contact Dermatitis
Contact dermatitis can cause loss of pigment in the nose.
We would like to express that, althought we understand that a dog lacking pigment is considered “incorrect”, we in no way suggest that this prevents these dogs from being wonderful family companions.
Here is a Labrador with incorrect pigment.