Clarifying Brown Egg Genetics

Discussion in 'General breed discussions & FAQ' started by Naamahbengals, Dec 2, 2013.

  1. Naamahbengals

    Naamahbengals Chillin' With My Peeps

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    Ok, asking a few more questions to clarify on the dominant brown egg genetic.

    So, it seems to be all up to the hen for brown color, not at all the egg. Is this correct? Since the hen produces the brown pigment on all of her eggs, no matter the roo that covers her.

    So, a hen that lays white or blue eggs will never produce brown eggs, even if covered by, say, a Marans or a Wyandotte, etc. Yes?

    Ok, hypothetical situation as follows.

    Brown is a dominant gene, and most purebreed brown layers have two copies of that gene. So if a brown layer (say, EE) was covered by a white-egged breed (say, Silkie) roo, then all chicks would only carry one copy of the brown layer gene (at most; if the hen for sure carries two copies). Yes?

    But - correct me if I'm wrong - there is no way to tell if a chick will be a homozygous brown, single carrier, or does not carry brown (therefore white or blue) layer by the color of it's egg, because momma hen is going to cover it in brown no matter what.

    And in reverse - this means that, if a roo carried the brown gene, he could pass it to his chicks, but those chicks could hatch from white or blue eggs (when paired to a non-brown layer) so you wouldn't know they carried. Right? (Or is it sex-linked, and the roo can't carry that gene?)

    So it seems, the ONLY way to know if a chick will give brown eggs, is to raise her up and see. And there is no way to tell for a rooster. Is this correct?


    Thank you for all of your help. We are currently trying to breed for blue eggs, through our EE hens and our Silkie roo. Next spring we will be buying cream legbar hatching eegs, and those hatched hens will be paired in... but we have a sentimental connection to our current EExSilkie pullets (our first home-hatched chicks, from our original and RIP silkie roo, who we loved), and we don't want to exclude them from the line. But we want to find the best way to exclude the brown gene in the shortest amount of time (generations-wise).
     
  2. Ridgerunner

    Ridgerunner Chicken Obsessed

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    You are correct. The rooster covering a hen has absolutely zero effect on the color of eggs that hen lays. That’s simple. But now it gets more complicated.

    Brown is not one gene. Last I heard there were 13 different genes that have been identified as contributing to brown with who knows how many not yet identified. Some are dominant, some are recessive, some are partially dominant, at least one is even sex-linked. That’s why you can get so many different shades of brown or green eggs. The shade of brown the hen lays on depends on which of those genes are present and how they interact with each other.

    Let’s do this:
    Blue + no brown = blue
    Blue + brown = green
    White + no brown = white
    White + brown = brown

    Since a hen that lays a white or blue egg doesn’t have any brown dominant genes, they won’t contribute any brown dominant genes. It’s always possible that hen has a recessive brown gene but you have to take some things on trust. A rooster doesn’t lay eggs so you don’t know what he is contributing to the gene pool, but if he comes from a flock that lays white or blue eggs, he is unlikely to contribute any brown.

    There are two ways to get to a bluer egg. First, you can only hatch the bluest eggs and select your breeders from those. Some brown may be imbedded in the gene pool so you can never totally get all the brown out, but you can get pretty close. It depends on what brown genes are in the gene pool and if they are paired up.

    The other way is each generation, cross your chickens that lay the bluest eggs with a blue or white egg layer. Eventually you can get to blue eggs though it is always possible you could have a recessive hiding under there that occasionally pairs up so don’t be too shocked to see some brown a few generations after you think you got it done.
     
  3. ChickenCanoe

    ChickenCanoe Chicken Obsessed

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    It is quite complicated and very little research has been done.
    If you're crossing there isn't a way to know what the offspring will bring to the table till they lay eggs.
    You can be fairly confident that if a rooster comes out of a brown or blue egg, his daughters will have those genes.
    I had a surprise crossing a Penedesenca roo with a Welsummer hen.
    Welsummer hen laid a very dark brown egg.
    Penedesenca rooster came out of an intense reddish maroon egg.
    Guess what the daughters laid - very light brown egg. This speaks to the number of genes that make up egg color. Apparently some from both parents negated each other.

    The color is applied by pigment cells toward the end of the shell gland though some can be earlier and applied with calcium so the color will be inside the shell rather than just outside.
    The ability to apply pigment belongs to the hen alone. In addition to multiple genes, there are multiple chemicals that make up the color.
     
  4. Ridgerunner

    Ridgerunner Chicken Obsessed

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    You can be fairly confident that if a rooster comes out of a brown or blue egg, his daughters will have those genes.

    Sorry, Canoe but I don’t quite agree with that statement. I’ll pretty much agree with the brown statement just because of the likelihood of several brown genes being involved. But just because the egg he hatched from was blue does not mean he got a blue gene.

    Consider a hen that is split for the blue gene, one blue and one white, and mate her to a rooster that is pure for white. She will at random give either a blue or a white to her offspring. In that case the odds are no better than 50-50 the rooster will have a blue gene. That’s not confidence.

    Consider a case where the hen and rooster both are split for the blue gene, each randomly giving a blue or a white. Odds improve a lot, from 50-50 to 75-25 that the offspring will have at least one blue gene, but that’s not assurance. With the randomness of genetics being passed down when they are split, there are not a whole lot of guarantees with this stuff. And with blue being dominant, it’s hard to know if the chicken is split for the blue gene or pure when it does show up.

    I like your example of the light egg coming from the two that should give dark eggs. It shows just how random it is when you mix all those random genetics.

    I’ve seen what you are talking about too on the brown being laid down with the shell. The simplistic approach is that the base color (blue or white) is laid down first and the brown is applied later as a top coat, but if you crack and egg and remove that inside membrane you can see the true color of that base color. I’ve seen a lot that are pretty pure white but I’ve also seen some that are more of an ivory color. You try to keep it simple so you can understand the concepts but there are always exceptions that just complicate it.

    I think that’s why the OP thought the brown color was one gene. Someone was probably trying to simplify the concept. Bengal’s logic was pretty solid if brown were just one gene, but unfortunately it’s not. It’s a mess.
     
  5. Naamahbengals

    Naamahbengals Chillin' With My Peeps

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    I knew the hen controlled the brown - but I was under the impression that the underlying color of the egg was controlled by the individual chick's genetics. So the hen decides all egg colors and what the chicks carry has nothing to do with their egg color? So, out of a hen that produces both green and brown eggs - I could get a chick from one of the brown eggs that still carries a copy of the hen's blue gene? If so, that will make quite a difference in what chicks I keep... I was planning on keeping only chicks from green eggs, and selling all chicks from brown eggs, to work towards blue. If the chick has no control over it's egg color, then I need to be keeping brown eggs too.
     
  6. Ridgerunner

    Ridgerunner Chicken Obsessed

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    Getting frustrating isn't it? I think I see your basic misunderstanding.

    The hen's genetics totally control the color of the egg she lays. Let’s simplify it. Don’t even think about brown and green. Think only white or blue. The blue gene is dominant over the white gene.

    The hen has two genes at that gene pair. If the hen has two blue genes at that gene pair, she will lay a blue egg. Since blue is dominant, if the hen has one blue gene and one white gene at that gene pair she will lay a blue egg. If the hen has two white genes at that gene pair, she will lay a white egg. Whatever genes the hen has at that gene pair determines what color egg she will lay.

    When the hen contributes her genetics to the egg, she gives a copy of one of those genes at that gene pair. Which gene she gives is totally random. If she has two blue genes at that gene pair, she will obviously give a blue gene and lay a blue egg. If she has two white genes at that gene pair, she will lay a white egg and contribute a white gene to the egg. Those are simple, but now it gets more complicated.

    If she has one blue gene and one white gene, she will lay a blue egg, but she might contribute a blue gene or a white gene to the egg. You cannot tell by looking at the egg what gene she gives to her offspring.

    Out of all this, there is only one thing you know for sure. If the hen lays a white egg, she will give a white gene to her offspring. So hatch your blue eggs.
     
  7. donrae

    donrae Hopelessly Addicted Premium Member

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    I may be wrong, but I don't think you can work backwards from green and brown and get blue. If you want blue, you need to start with blue. Someone correct me if I'm wrong.

    A hen always lays the same color egg. Her egg shell color is determined by her genetic make up, has nothing to do with a rooster mating her or a chick developing in that egg.

    Each chick gets half it's genes for egg color from each parent, just like any other genes.
     
  8. Naamahbengals

    Naamahbengals Chillin' With My Peeps

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    I'm also working with white-layers, paired with green-and-brown layers (hen and roo, obviously); so I can get blue from a green layer line, eventually. I will be adding in Cream Legbar to help. I could just work with the white layers and the blue layers, yes... but I have an emotional connection to the hens sired by my now-dead Silkie Roo (who I loved), so I am going to continue to work with them as well. Makes it harder for me, sure, but I love these little guys. :p
     
  9. ChickenCanoe

    ChickenCanoe Chicken Obsessed

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    Very good simplification. I like it.

    Unless it is one of those dark layers that applies multiple pigments. Occasionally, often late in the laying season, not all of those chemicals are available. I can get very dark eggs most of the time and all of a sudden a hen will start putting out one or a couple weeks worth of light eggs.
    I assume that situation is nutrition related.
     
  10. Naamahbengals

    Naamahbengals Chillin' With My Peeps

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    Does this mean, a single color? I could swear that my EEs were laying both green and brown eggs, from the same hen.
     

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