Liver noses and tyrosinase
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Thread: Liver noses and tyrosinase

  1. #1
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    DefaultLiver noses and tyrosinase

    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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    Canyon Labradors's Avatar
    Canyon Labradors is offline Senior Member
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    DefaultRe: Liver noses and tyrosinase

    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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    mollyrock's Avatar
    mollyrock is offline Senior Member
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    DefaultRe: Liver noses and tyrosinase

    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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    DefaultRe: Liver noses and tyrosinase

    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.

  7. #5
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    DefaultRe: Liver noses and tyrosinase

    Molly that's pretty common it's called a Winter or Snow Nose.

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    mollyrock's Avatar
    mollyrock is offline Senior Member
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    DefaultRe: Liver noses and tyrosinase

    yeah, I know..but Lucy has liver pigment..I am talking about whether or not a liver nose fades.


  9. #7
    WigWag Guest

    DefaultRe: Liver noses and tyrosinase

    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.

  10. #8
    WigWag Guest

    DefaultRe: Liver noses and tyrosinase

    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.

  11. #9
    WigWag Guest

    DefaultRe: Liver noses and tyrosinase

    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:



  12. #10
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    DefaultRe: Liver noses and tyrosinase

    Quote Originally Posted by Indiana
    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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