True or False? Olive egg genetics.

[The Moonshiner]

Cross of Brown X Blue is not going to give precisely the same result as crossing Blue X Brown. Reciprocal crosses are affected by the W/Z chromosomes as some of the genes in the porphyrin biopath are on the sex chromosomes.

That said, you can still generalize that crossing a blue egg layer X a brown egg layer and carrying forward to the F2, 1 in 16 will lay white eggs, 3 in 16 will lay some shade of brown egg, 1 in 16 will lay some form of blue egg (caused by recombination of the blue and white genes where the white gene disables the porphyrin biopath), and 11 in 16 will lay some form of egg carrying the blue egg gene with varying overlay of porphyrin producing olive green, teal, spearmint green, tan green, or other slightly nuanced color on top of the blue egg shell.

Moonshiner is partially correct that it is very difficult to recover blue egg layers from crosses with brown egg layers, however, it can be done if you raise enough birds and have enough generations to select. Note from the above that 1 in 16 will lay blue eggs. This means you have to raise 32 chicks (half male, half female) to find one female that lays blue eggs. Even then, she may have only one copy of the blue egg gene as it is dominant. Remember that blue eggs are from a combination of white egg base color with the oocyanin gene. To give a comparison, after eliminating all brown egg layers from my flock, I have about 16 hens currently laying of which 2 lay blue eggs. I did a lot of culling to find those two blue egg layers. The blue egg layers have flaws in terms of feather color and/or type. I have to keep breeding to eventually stabilize silver laced blue egg layers.

 

[The Kooky Kiwi]

Not as much sense as i wish, but thats due to my lack of understanding, not your explanation.

Here's an alternative (less genetic speak) explanation:

A basic egg shell starts as white.
Blue egg genes alter the actual shell color from white to blue.
Brown egg genes do not alter the underlying shell color but rather they paint over that shell color.

Your final egg color depends on the presence of absence of the various egg colouring genes.

No Blue Genes + Yes Brown Genes = Varying shades of brown (on a white shell)

Yes Blue Genes + Yes Brown Genes = Varying shades of brown (on a blue shell) - giving varying shades of Olive/Green eggs.

Yes Blue Genes + No Brown Genes = No shades of Brown (on a blue shell) - giving a blue egg.

There are also genes that affect "location" of some of the color deposits = resulting in speckles on the eggs.

And then there is a "bloom" - which I understand isn't actually a color at all but a sort of lacquer or coating (the others can correct me there if that's not quite right). This can slightly alter the "tint" of the finished egg colour - often giving a pinky look.

 

[Allsfairinloveandbugs]

I reread everyones input again just now. Thank you all. I now know my (lack of) understanding of egg color genetics went off-track years ago. When i got Easter Eggers (yes they were sold as Ameraucanas, but 2/3 of the foundation flock of 24 did lay blue eggs, & laid very well). I started researching egg color genetics on Many websites, not just byc. Somewhere out there in internet land still exists the info i absorbed as "fact." There was never a mention on that site of a white egg gene when discussing blue eggs. What was stated as fact was that a blue egg carries 2 blue genes. Period. And a green egg carries one blue gene and one brown gene. Period. And a brown egg carries 2 brown genes. I repeat, a white egg gene was Never mentioned. Aaaaaaaargh!

I have had white egg layers show up in the generations of hatchees. But i thought that was due to crossing in white leghorn eggs (to increase egg size) and blue andalusian eggs (to introduce blue feathers) in years past.

So now i know i know even less than i thought i knew. And feel Very lucky the blue egg gene wasn't lost. The easter eggers are my "forest gump box of chocolates", never know what color im gonna get. If someone asks about a specific color, theyve probably laid it. Been getting purple eggs from the 2020 girls. I Think the purple is extra bloom on a brown egg? No clue who is laying them, or how to reproduce it, but still really neat to see!

Below is photo of the blue and purple eggs being laid this year. The two in the middle appear a true purple color, while the others are a purplish-brown. That the reason i think they are coming from 2 different pullets. Thanks again for the explanations!

 

[The Moonshiner]

I reread everyones input again just now. Thank you all. I now know my (lack of) understanding of egg color genetics went off-track years ago. When i got Easter Eggers (yes they were sold as Ameraucanas, but 2/3 of the foundation flock of 24 did lay blue eggs, & laid very well). I started researching egg color genetics on Many websites, not just byc. Somewhere out there in internet land still exists the info i absorbed as "fact." There was never a mention on that site of a white egg gene when discussing blue eggs. What was stated as fact was that a blue egg carries 2 blue genes. Period. And a green egg carries one blue gene and one brown gene. Period. And a brown egg carries 2 brown genes. I repeat, a white egg gene was Never mentioned. Aaaaaaaargh!

I have had white egg layers show up in the generations of hatchees. But i thought that was due to crossing in white leghorn eggs (to increase egg size) and blue andalusian eggs (to introduce blue feathers) in years past.

So now i know i know even less than i thought i knew. And feel Very lucky the blue egg gene wasn't lost. The easter eggers are my "forest gump box of chocolates", never know what color im gonna get. If someone asks about a specific color, theyve probably laid it. Been getting purple eggs from the 2020 girls. I Think the purple is extra bloom on a brown egg? No clue who is laying them, or how to reproduce it, but still really neat to see!

Below is photo of the blue and purple eggs being laid this year. The two in the middle appear a true purple color, while the others are a purplish-brown. That the reason i think they are coming from 2 different pullets. Thanks again for the explanations!

Ok now that you have it all figured out let me add that there's also a gene I believe is sex linked recessive that inhibits the brown genes. A lot of leghorns carry it.

 

[Allsfairinloveandbugs]

Never heard of a sex-linked recessive brown gene inhibitor either. I will research that out of curiosity, but doesnt mean i will understand it. I have Nothing figured out. Guess i ll keep taking the Forest Gump approach with egg colors. And will keep trying to understand more about feather color genetics on your leghorn thread.

 

[The Kooky Kiwi]

I reread everyones input again just now. Thank you all. I now know my (lack of) understanding of egg color genetics went off-track years ago. When i got Easter Eggers (yes they were sold as Ameraucanas, but 2/3 of the foundation flock of 24 did lay blue eggs, & laid very well). I started researching egg color genetics on Many websites, not just byc. Somewhere out there in internet land still exists the info i absorbed as "fact." There was never a mention on that site of a white egg gene when discussing blue eggs. What was stated as fact was that a blue egg carries 2 blue genes. Period. And a green egg carries one blue gene and one brown gene. Period. And a brown egg carries 2 brown genes. I repeat, a white egg gene was Never mentioned. Aaaaaaaargh!

I have had white egg layers show up in the generations of hatchees. But i thought that was due to crossing in white leghorn eggs (to increase egg size) and blue andalusian eggs (to introduce blue feathers) in years past.

So now i know i know even less than i thought i knew. And feel Very lucky the blue egg gene wasn't lost. The easter eggers are my "forest gump box of chocolates", never know what color im gonna get. If someone asks about a specific color, theyve probably laid it. Been getting purple eggs from the 2020 girls. I Think the purple is extra bloom on a brown egg? No clue who is laying them, or how to reproduce it, but still really neat to see!

Below is photo of the blue and purple eggs being laid this year. The two in the middle appear a true purple color, while the others are a purplish-brown. That the reason i think they are coming from 2 different pullets. Thanks again for the explanations!

It can be difficult can't it! Trying to learn something by reading the grand library that is the internet I'd say the information you found, was the old understanding of things that has since been superseded because we now have such a better understanding of how genetic things work. Perhaps a kinder way is not to say that information is "wrong" but rather to say it is "outdated"

In respect of the white egg colour - no there is no gene for a white egg. That's just your basic natural starting color if you like. The body puts together all the components for an egg and in the absence of any gene that tints or paints that egg - it remains basic white.

When discussing the genetics we always describe in terms of pairs because that is how gene traits are received from their parents (one from mom and one from dad).
For Example:

An Araucana has two blue genes in their pair which is expressed Blue / Blue

An Easter Egger receives the blue gene from their Araucana parent only - meaning there is only one blue gene in their pair. This is expressed Blue / -

The "-" symbol means there is no modifying gene - aka this part of the gene pair defaults to white.

A bird with a gene pair - / - has no modifying genes at all and lays a white egg.

Let's use those basics to describe a Bird that lays Speckled Olive Eggs.

Blue / Blue = Blue base egg shell PLUS
Brown / Brown = Brown pigment over that base egg shell PLUS
Speckles / Speckles = Speckles over the base and pigment

Now.. the coooool thing about the blue gene is that your bird only needs to have one copy for it to still work! (read up on dominant traits and how they work)

While this is eggsellent for those of us who love Easter Eggers and blue eggs - we do have to remember that when we breed from those birds they only themselves can pass the blue gene down to 50% of their chicks. The other 50% of their chicks receive the "-" half or white egg possibility. You then have to take a look at your roosters egg genetics to make an intelligent go at what egg genes he will contribute to the chicks. If he is also from white egg laying stock - then you will get some chicks that are white egg layers.

 

[The Kooky Kiwi]

... Sex linked recessive that inhibits the brown genes. A lot of leghorns carry it.

Dominant Trait = one copy is needed to express itself
Recessive Trait = two copies are needed to express (if one copy is there it is "hidden")
Sex Linked Trait = A male needs two copies to express the trait, a female only needs one copy to express the trait.

So thinking back to those "pairs" of genes in my earlier example - Blue is a dominant trait so it "shows" or "expresses" when only one gene is present in the pair.

Moonshiners example above says that if a female bird receives ONE copy of that gene then it will act to "inhibit" or "hide" or "turn off" any brown egg genes that are also present for that bird.

Using my previous method you could also look at Moonshiners example this way:

No Blue / No Blue = White base egg shell PLUS
Brown / Brown = Brown pigment over that base egg shell PLUS
Recessive Inhibitor / Recessive Inhibitor = Turns Off or Cancels Out the Brown Above

Results in a bird that "technically" does contain brown egg genes but lays a white egg anyway.

 

[Allsfairinloveandbugs]

Thank you for the very detailed and clearly explained info, @The Kooky Kiwi . I think/hope your explanations will help those who discover this thread in the future gain a more clear understanding too. I guess it is possible the info i initially read was "outdated" rather than plain out wrong. Either that, or you are just being very nice.

I have a couple of followup questions. Re blue eggs, i did understand that blue is dominant, which is why i wasnt too concerned about introducing leghorn and andalusian eggs. And i understand that ameraucanas and auracaunas carry blue genes only. What i'm unclear on is, are you saying an Easter Egger cannot carry Blue/Blue? Ive never purchased easter eggers since the original 2 dozen in 2014. All generations since then have been home-hatched. If many of those original blue egg layers were not Blue/Blue (the 4 easter egger roos were purchased at same time), it seems almost impossible i would still be getting blue egg layers. If i had known, as @DarJones said, that F2 crosses only result in 1/16 blue egg layers, i would have kept the blue layers separate, and probably never crossed with brown egg layers in the first place.

My question about speckled eggs is shorter. Are you saying in order to have speckles, an egg needs speckled genes from Both parents? As in Speckled/Speckled, not Speckled/-- . ? My original brown speckled egg layers were Welsummers. An Easter Egger/Welsummer roo was the flock leader for 3 years, and he produced a lot of olive eggers. If it takes speckled egg genes from both sides to produce speckled eggs, he was the other source. Photo below is of olive eggs & Welsummers. Not all are speckled, but many are. I have no memory if the Easter egger roo/welsummer hen f1 crosses laid olive speckled. Genetics may be complicated, but it is also very fascinating.

The recessive inhibitor gene info is very intereresting too. I will follow up with that on the Moonshiner's thread.

 

[The Kooky Kiwi]

I have a couple of followup questions.

Re blue eggs, ... are you saying an Easter Egger cannot carry Blue/Blue?

Yes - clarificiation is needed there - I used the term Easter Egger to mean a chick or cross or descendent from an Araucana (or Americauna dependent on where you are) that has been bred to another non Araucana breed. In my head an Easter Egger describes a Non-Pure breed bird - but of course the "reason" people breed them is to get the blue eggs so that is why I referred to it in my example - since I wanted to talk about blue egg genes.

To avoid confusion - I might continue with the terminologies "Blue Egg Layer" or "Olive Egg Layer" for clarity

To answer your question above:
Let's take a blue egg laying hen with double blue egg genes (Blue / Blue) and breed her with a rooster with white egg genes ( - / - ),
Mom will contribute one blue gene to 100% of the chicks
Dad will contribute the "-" gene to the chicks.

So 100% of your chicks will be (Blue/-) Blue egg layers.

If your mom hen above was an Araucana (Americauna depending on location) and your rooster was something else - We would commonly call their chicks "Easter Eggers".

Let's take one of their rooster babies and see what happens if we breed him to a blue egg laying hen of another breed (non Araucana) (so moving from the F1 generation to the F2 generation)

Rooster baby from above that contributes (Blue / -)
Blue egg laying hen contributes (Blue / Blue)

Half of the chicks will be (Blue/Blue) and the other half (Blue/-)
They are all still blue egg layers so yes it is possible to achieve second generation "mixed breed" babies that are blue egg layers with Blue/Blue genetics. You just have to select the right birds that are known to carry the blue egg genes.

When you do these mixed breedings and combine blue egg genetics with brown egg genetics - that's where you get babies that produce "Olive Eggs" called "Olive Eggers".

My question about speckled eggs is shorter. Are you saying in order to have speckles, an egg needs speckled genes from Both parents?

I'm actually not that familiar with the "speckled" genetics - I do not have it at all in my flocks. That's a question best posed to the BYC community that have speckled egg layers But I did want to mention it so that you had an example of another "effect" that can be seen on the eggs. Some people deliberately breed for the speckles - they're kinda cool!

 

[DarJones]

no there is no gene for a white egg.

When it comes to chickens and genetics, never say never. If you delve deep into Leghorn genetics, there is a gene that causes the intense zinc white color of their eggs. This gene is not present in many white egg layers. They lay eggs that are more of a washed out white. I've seen this washed out white quite often in Red Games. I have not tried to sort this gene (zinc white) out in terms of which chromosome it is on. It is possible it is sex linked as suggested by Moonshiner. I can prove this gene is penetrant meaning that it always shows up when present, but that it is otherwise neither dominant nor recessive. When homozygous, it gives maximum expression. Zinc white eggshells are significantly stronger than washed out white shells.

So to state what I have seen in my birds, The base eggshell color is always white. This is true for all chickens regardless of other color modifications. There is a gene for Zinc White in Leghorns and other mediterranean breeds that results in intense white eggs. The gene(s) for intense white strongly suppress porphyrin production such that any cross of a chicken with the zinc white trait crossed with a brown egg layer will lay an egg tinted very light tan. It may be tan on top of white or it may be tan on top of blue, but it is always light tan. When the genes segregate in the F2 generation, the traits will wind up in the ratio I gave earlier. F2 means to make a cross (Blue/white X Brown) and keep both roosters and hens. Then intercross ((Blue/white X Brown) X (Blue/white X Brown)) to get the F2.

Re having blue egg layers over multiple generations, this is easily done if you cross back to a rooster that carries the pure blue egg trait (white eggshell with oocyanin on chromosome 1). If you do as I did and cross repeatedly to a brown egg layer (Silver Laced Wyandotte is the recurrent parent of my chickens), you will suppress the genes that disable porphryrin so far into the background that it is very difficult to recover a pure blue egg layer. This is why I value the two blue egg layers I have so much. My ultimate goal is to turn off the porphryin genes leaving my chickens laying pure blue eggs with the zinc white trait from the leghorn parent and with no porphryin coating. I also select strongly for large eggs with my goal to have 55 grams or larger. I have quite a few chickens laying 40 to 50 gram eggs currently so have a lot of work to do to select larger.

It usually blows peoples minds when I tell them I crossed a blue egg layer X a brown egg layer and got white eggs in a few of the F2 birds. All it means is that I got the combination of (b/b - no blue genes) plus (pph/pph - no porphryin) plus (zw/zw - zinc white eggshell). As I noted, the ratio of white egg layers is 1 in 16. This tells me there are at least 2 genes involved in turning off the porphryin biopath. Caution that this applies to my birds. Other genetics could easily give different results.

One caution, as I mentioned in another post elsewhere, there is a chromosome deletion in some lineages that turns off the porphyrin biopath. If you get tangled up with the chromosome deletion, the result is significantly lower egg production and smaller than normal eggs. Based on investigation I did several years ago, I suspect the deletion is present at a low rate in some strains of Legbars. This is not proven, it is just very suspicious that efforts to intensify the blue egg trait in legbars results in fewer and smaller eggs laid. That sounds very much like the result of the deletion.

There was never a mention on that site of a white egg gene when discussing blue eggs.

Technically, there really isn't a white egg gene. All chickens have the porphyrin biopath meaning that they have the genetic machinery to produce brown coating on eggs. Some chickens have one or more genes that disable the porphyrin biopath which makes the base white eggshell color express. So it is not so much a gene for white as it is a gene(s) that disable brown. Since the base eggshell color is white, if brown is turned off, the white shell is what we see.