Question about genes for blue egg laying?

[Gypsy07]

I just saw an auction on ebay UK where someone is selling hatching eggs from their ISA Browns and Black Sexlink hybrid hens. Their rooster is a Cream Legbar. The price is quite high for mutt eggs as the selling point of their auction is that all chicks from these eggs will inherit a dominant gene for blue egg laying. The seller states 80% of pullets hatched by themself from this cross lay a blue egg and 20% lay a green egg. I know very little, well, nothing actually, about the genes for egg colour. Is this correct? For some reason I smell a rat...

 

[dsqard]

I am still learning about the blue egg gene but I would suspect that those numbers are backwards at best. From what I understand, if you cross a blue egg layer with a brown egg layer you get a green egg layer. For the egg to be blue, the chicken would have to carry two copies of the blue egg gene for it to lay blue. Unless the seller is crossing the roo with his daughters, there is no way they could be getting two copies of the gene.

 

[Gypsy07]

Yeah, I suspected something like that. I wasn't thinking of buying them, I just wondered about the truthfulness of the seller's claim. There is a small note at the bottom of their listing that says a "very small percentage" of birds hatched will lay brown eggs due to inheriting the recessive alleles for brown egg laying. Hmph!

 

[Sonoran Silkies]

Quote:
No.

A single copy of O (the blue eggshell gene) will cause a female to lay eggs with blue eggshells. The cream legbar can be assumed to be pure for O (meaning htat it has two copies) so ALL its offspring will inherit a copy of the gene. Yes, if the legbar is crossed with his daugters, they may have two copies of the gene, which may deepen the shade of the blue eggshell.

Green eggs are formed when the hen deposits a brown coating on the outside of the eggshell. There are many genes involved in this, not just one, and can vary from barely tinted to a very dark-chocolate shade. A hen whose eggshell is white, and that also deposits a brown coating will lay a brown egg. Those whose eggshell is blue, and deposit a brown coating lay a green egg. I could speculate that a very lightly tinted egg, which often looks pinkish, would look more blue than green if the eggshell is blue. But is the hue of the coating is more brown, the egg would look more like green.

Depending on the genes for the brown coating carried by the Isa Browns and the black sex-links blue eggs are possible. Isa Browns should lay brown eggs, but in googling, I came up with a number of instances where they lay white. Black sex-link is a generic term; depending on the particular breeds crossed, it would be possible to have ones who lay white eggs. Probably not usual, but possible.

Questions to ask the seller are whether the hens are first, second or subsequent generations of this cross. Also, ask for photos of the blue and green eggs. Are the eggs you would be getting going to be white, brown, blue or green? If the eggs are laid by hens who are not crossed with the legbar, the colour of the egg will tell you at last half of the genes they are likely to inherit for white vs brown coating. If they already have the blue egg gene, the egg colour will tell you the same--just lookk at it as blue vs green raher than white vs brown.

 

[Gypsy07]

Wow, that's a lot of information. Thanks for going into so much detail here. The black sexlinks were Black Rocks, which is a UK hybrid of RIR cockerel over Barred Rock hen. I have a few myself, and they lay a light brown egg that is sometimes lightly speckled. The seller states that all the eggs for sale are brown , but that the chicks from these eggs will be blue or green egg layers. From all the information you've given me, I guess that won't be true! These aren't eggs that I was thinking of buying btw, I was just really interested in whether the seller was genuine or not. I don't know much about the genetics of egg colour and as always, I knew here on BYC would be the best place to get an explanation!

 

[Sonoran Silkies]

If all the eggs are brown, I doubt you would get any BLUE eggs from the offspring. Green, yes, but not blue.