True or False? Olive egg genetics.

[TheOddOneOut]

Some other chicken keepers told me something interesting. I wasn’t sure if it was true or just something they had been told, but...
Anyways, this is the basis of it:
When you cross a blue layer with a brown layer, you get green eggs. And if you breed a f1 hen and a rooster of this cross, you can‘t get more green eggs. They are only blue or brown.
They also muttered something about “true olive eggers” being different.
I was skeptical, but I thought I would ask you all.
Thoughts?

 

[The Moonshiner]

Not true.
The F1 crossed will give you 75% green eggers and 25% brown eggers.
The brown egg genes are different genes then the blue/white shell genes and it's said there's 13 or more genes that could be involved.
Once you cross in brown it is very hard to get rid of it so it's very unlikely to get back to any blue eggers.

 

[The Moonshiner]

Some times it's best to leave things be. Never know where it could end up.

 

[FuzzyCritters]

False. When you cross the F1s, 75% of the offspring will have blue shells and 25% will have white shells. They will inherit varying amounts of brown pigment, so the eggs will be varying shades of tan, brown, green, and teal.

I don't see the logic in what the people told you. If the potential exists for brown eggs in the F2s, the potential must exist for green eggs as well.

 

[The Moonshiner]

Wait im confused. I know without a doubt you know your genetics. But how can the blue egg gene completely disappear? I thought the above f1 crosses would result in approx. 25% blue, 50% green, & 25% brown?

If a f1 hen carries 1 blue egg gene and one brown egg gene, and a f1 roo does also, wouldnt that mean a 25% chance of getting a f2 with 2 blue egg genes?

There's two sets of genes involved.
The shell color genes are simple either blue or non blue (white) Blue is dominate.
The other set is for brown or lack of. There's many genes. At least 13 for the brown coloring. Hence why there's so many shades of brown.
Most brown egg layers carry several of those genes so once you bring it into the mix its hard to get a cross that would happen not to get at least a few.
Make sense now?

 

[DarJones]

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.

 

[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.

 

[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.

 

[TheOddOneOut]

That’s what I thought! I may kindly explain this to them, I may not. But thanks anyways!

 

[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.