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I've been reading about the color variations in labs and I know that the production of tyrosinase in yellow labs with black pigmentation affects how dark or light the nose is, and I know that true dudleys have a permanently pink nose, I was wondering about liver colored noses, I know this is caused by a yellow dog that carries the chocolate gene, but I don't know if they are also affected by tyrosinase. Do liver noses lose their pigmentation and fade like black noses due to age and climate? Or do they stay liver colored? Does it depend on whether the dog is yellow or chocolate?

This may be a stupid question, but I'm curious and not afraid to look stupid ;D. Based on what I've read, it would make sense for them to fade, because tyrosinase determins melanin levels and that determines pigmentation, and I think all animals have melanin ... but every time I see the fading mentioned they specifically talk about black noses on yellow labs.
 

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Liver noses stay liver. It's basically a yellow lab with the skin coloration of a chocolate lab. It actually has nothing to do with a dudley, though many just call it that for sake of ease. I have three chocolates and NONE of their noses have ever faded.
 

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I don't know the answer to your question.
It might be my imagination but Lucy's liver pigment seems more pink in the winter than in the summer.
 

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Both true dudleys (pink pigment) and chocolate pigmented yellows have the same genotype, eebb...neither carry black. All yellow coated dogs' nose pigment fades to some degree with age, whether it be chocolate or black pigment. Pigment in chocolate coated dogs doesn't change all that much...similar to black pigment on black coated dogs.
 

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Molly that's pretty common it's called a Winter or Snow Nose.
 
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A Dudley is a Dudley is a Dudley. No difference between a yellow with a "pink" nose or a "liver" nose and lips and eyerims. A yellow with correct black pigment that has a nose that fades is different. Some Dudleys are cream colored with lighter pink/flesh colored noses and skin and others are darker coated with darker brown pigment. The genes for yellow, chocolate, and black are the same - eebb. Now that said I have a Dudley whose nose does get darker brown in the summer and lighter in the winter and now Molly says the same of hers. There has never been an informal study of whether or not Dudleys' noses fade to my knowledge but I'm betting yes.
 
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Both true dudleys (pink pigment) and chocolate pigmented yellows have the same genotype, eebb
The original Dudley bulldog was simply a red and white dog with a liver nose - nothing to do with pink or liver coloration. They didn't understand the genetics behind this back then and labeled the color combination a "lack of pigment" even though it was simply a liver pigmented dog. This translated to the Labrador breed standard as a Dudley being a dog that lacks pigment. That has now been proven to be a wrong use of those words.
 
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Both of these dogs are Dudley yellows or liver pigmented yellows. Molly's Lucy (I hope it's okay to repost this photo - let me know if not) is a light colored dog and has a corresponding light brown pigmentation. My Cuffy is a dark yellow and has brownish pigment. Both dogs are eebb (yellow and chocolate with no black). Many people would call Lucy a Dudley and say Cuffy has brown pigment and is therefore not a disqualification and could be shown. Which is it? You can't disqualify one and not the other - they are the same. Neither "lacks pigment" and both have brown pigment albeit different shades.






Cuffy in the summer - notice his nose is darker than in the above pic taken in the winter:
 

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Indiana said:
I've been reading about the color variations in labs and I know that the production of tyrosinase in yellow labs with black pigmentation affects how dark or light the nose is, and I know that true dudleys have a permanently pink nose, I was wondering about liver colored noses, I know this is caused by a yellow dog that carries the chocolate gene, but I don't know if they are also affected by tyrosinase. Do liver noses lose their pigmentation and fade like black noses due to age and climate? Or do they stay liver colored? Does it depend on whether the dog is yellow or chocolate?

This may be a stupid question, but I'm curious and not afraid to look stupid ;D. Based on what I've read, it would make sense for them to fade, because tyrosinase determins melanin levels and that determines pigmentation, and I think all animals have melanin ... but every time I see the fading mentioned they specifically talk about black noses on yellow labs.
Just another curious question to add to yours ... how is this all affected by diet and exercise? I have experience with only one varying nose (Ivy's), but I swear that diet and exercise have a stronger affect on her pigment than season and age. We switched her food a little over two years ago, and her pigment darkened significantly ... ditto when we added a supplement to her diet ... ditto again when we moved into a home in the woods (increasing daily exercise). Is this a possibilty, or a coincidence?

P.S. My siggy picture is Ivy no more than 2 weeks ago ... 8 years old, middle of February, and darker pigment than years past.
 

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WigWag, is this your article on the Woodhaven web site? http://www.woodhavenlabs.com/yellow-pigment.html

The second half of the article contradicts the first half, which is part of what prompted me to read further (I see now that the article was compiled by both Wig Wag Labradors and Woodhaven Labradors).

Many say a yellow with liver pigment is a Dudley. It depends on the person and their definitions. The AKC describes it as flesh colored. In Anna Katherine Nichols book of the Labrador Retriever, written in 1983, the Dudley nose is defined as flesh colored.

The LRC defines a Dudley as pink. A yellow with chocolate pigment, whether its light or dark, is not a Dudley. It should be penalized, but not disqualified.

The AKC standard states:
The DQ for pigment reads, "A thoroughly pink nose or one lacking in any pigment."

In the Canadian standard, it states that the yellow's pigment is black or dark brown. Anything else is a serious fault (as the Dudley nose in the US had been throughout history).

A yellow with a brown/chocolate nose is NOT lacking in pigment, so they are not a Dudley and should not be referred to as such.



And I found this on the Wikipedia site

Lab nose and skin pigmentation

A Dudley Labrador Retriever. The nose and lips are pink or flesh-colored, the defining aspect of Dudley pigmentation, as compared to the more standard brown or black.Because Lab coloration is controlled by multiple genes, it is possible for recessive genes to emerge some generations later and also there can sometimes be unexpected pigmentation effects to different parts of the body. Pigmentation effects appear in regard to yellow labs, and sometimes chocolate, and hence the majority of this section covers pigmentation within the yellow lab. The most common places where pigmentation is visible are the nose, lips, gums, feet, and the rims of the eyes, which may be black, brown, light yellow-brown ("liver", caused by having two genes for chocolate),[15] or several other colors. A lab can carry genes for a different color, for example a black lab can carry recessive chocolate and yellow genes, and a yellow lab can carry recessive genes for the other two colors. DNA testing can reveal some aspects of these. Less common pigmentations (other than pink) are a fault, not a disqualification, and hence such dogs are still permitted to be shown.[15]

The intensity of black pigment on yellow labs is controlled be a separate gene independent of the fur coloring.[15] Yellow labs usually have black noses, which gradually turn pink with age (called "snow nose" or "winter nose"). This is due to a reduction in the enzyme tyrosinase which indirectly controls the production of melanin, a dark coloring. Tyrosinase is temperature dependent - hence light coloration can be seasonal, due to cold weather - and is less produced with increasing age (2 years old onwards). As a result, the nose color of most yellow labs becomes a somewhat pink shade as they grow older.[16] [15]

A coloration known as "Dudley" is also possible. Dudleys are variously defined as yellow labs which are unpigmented (pink) (LRC), yellow with liver pigmentation, or "flesh colored" (AKC), rather than having black or brown pigmentation.[15] A yellow lab with brown or chocolate pigmentation (for example, a brown/chocolate nose), is not a Dudley. Breed standards for Labradors considers a true Dudley to be a disqualifying feature for a show lab ("Disqualification: A thoroughly pink nose or one lacking in any pigment"). True Dudleys are extremely rare.[15][17][18] (See: Albinoism).

Breeding in order to correct pigmentation often lacks dependability. Because color is determined by many genes, some of which are recessive, crossbreeding a pigmentationally non-standard yellow lab to a black lab may not correct the matter or prevent future generations carrying the same recessive genes. That said, pigmentation is often not an issue with animal lovers for whom such issues are often unimportant, and only has significance for those involved with showing and breeding.




And this from http://www.labradornet.com/labradors.html

Alright, so what is the nitty gritty on coat color inheritance?
Two sets of genes, not one, control a Lab's coloration. One set of genes controls whether the Lab will be dark (either black or chocolate) or light (yellow). Dark is dominant over light. Thus a Lab whose genotype is EE (homozygous dominant) or Ee (heterozygous) will be dark; only Labs that are ee (homozygous recessive) can be light.
The second set of genes only come into play if the Lab is dark (either EE or Ee). This set controls whether the Lab is black (the dominant trait) or chocolate (the recessive trait). Thus, a dark dog (ie. EE/Ee) that is BB (homozygous dominant) or Bb (heterozygous) will be black, while the only way a dog can be chocolate is for it to be dark (EE/Ee) AND bb (homozygous recessive).

So now, the possibilities for black dogs are EEBB, EEBb, EeBB, or EeBb. The possibilities for a yellow dog are eeBB, eeBb, or eebb. And the possibilities for a chocolate dog are EEbb or Eebb. Remember that puppies will get one E/e from the dam and one from the sire, as well as one B/b from the dam and one from the sire to make up their complete "code". If you had two parents that were both EeBb (black in appearance), you can get all three colors in the resulting litter! Furthermore, when you realize that a pair of yellows can only give their puppies the ee combination, you understand why two yellows only produce yellows. In a similar fashion, two chocolates can only bequeath bb to their puppies, so two chocolates can never produce a black puppy.

The eebb is an interesting case, as this is a yellow dog with chocolate pigmentation on its nose and eyerims. A dog that is bb always has this pigmentation. Under the current standard, a yellow with chocolate pigmentation is disqualified.

If the Lab is mismarked, for example Black and Tan, or brindled, there are other allelles present in that dog's makeup. If you are interested in a further discussion of these genes, do look up Clarence C. Little's classic book, The Inheritance of Coat Color in Dogs.

What is a Dudley?
This is a yellow Labrador with chocolate pigmentation (eebb). It can also refer to a Lab with absolutely no pigmentation on the nose or eyerims (all pink in color), but in actuality, this is extremely rare, and probably a genetic abnormality.


And I read this slide show which was fascinating http://www.labradornet.com/labradors.html

I'm thoroughly confused now ;D It seems the label "dudley" is a subject upon which there is some disagreement.

In the interest of full disclosure :) my pup has the liver coloring and eyes that look green in natural light, yellow indoors, I assume that's probably similar to a chocolate's eye color. I don't think his nose has faded, but he's also in his first winter, so who knows. It's not important, it's just the more I read on this subject of coloring in yellows, the more questions I had :)

Here's a picture showing his coloring at about ten weeks.






By the way, all of your dogs are beautiful! And Jen, I love your sig :)
 

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Just another curious question to add to yours ... how is this all affected by diet and exercise? I have experience with only one varying nose (Ivy's), but I swear that diet and exercise have a stronger affect on her pigment than season and age. We switched her food a little over two years ago, and her pigment darkened significantly ... ditto when we added a supplement to her diet ... ditto again when we moved into a home in the woods (increasing daily exercise). Is this a possibilty, or a coincidence?

P.S. My siggy picture is Ivy no more than 2 weeks ago ... 8 years old, middle of February, and darker pigment than years past.
Hi, I realise this is an old thread but would you be able to tell me what the diet change entailed, and what the supplement was? I have a Dudley and I’d like to change her to a raw diet and wondering if that will affect her colouring. Thanks
 
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