Talk to me of egg color genetics

[Sonoran Silkies]

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Wow! I hadn't heard this before. Why does selecting for color intensity end up selecting for less or smaller eggs? I am interested because I am really interested in intense egg colors.
.......As for diet, I've seen discussions on this but I don't think anyone has managed to find a direct correlation between feeding a certain thing and getting great egg color. Although a good healthy diet helps keep the bird healthy, which probably does help with egg color. I've read about feeding Marans pigeon grit but haven't tried it.

I think Henk meant that with smaller eggs YOU would be going on a diet

I guess my question would be not about selecting to get darker/more intense colour, but rather WHY some birds have the darker more intense colour than others with the same genes. I know blue is related to bile; don't recall offhand what the brown egg colour is related to chemically in the bird.

Anyways, presumably anything that affected the bile would also affect blue egg colour? Or not?

PS--I think Miss Prissy was referring to recognised varieties of chickens, not the genetics of egg colour and whether they are hom or het for various egg colour genes.

 

[enola]

What has bile got to do with egg color ?

The spleen is not a part of the reproductive tract . . . . .

 

[Sonoran Silkies]

Well, what does calcium have to do with the reproductive tract, either?

It is fairly well documented that the pigment for blue eggshells is related to bile (from the liver, not the spleen).

"The brown pigment, ooporphyrin, is deposited primarily on the outside of the eggshell and is a chemical compound resulting from hemoglobin metabolism. In fact, much of the brown pigment can be buffed off with a common kitchen (plastic) scrubbing sponge and warm soapy water. The blue eggshell pigment, oocyanin, is a byproduct of bile formation and is present throughout the eggshell." and "The blue color is fundamentally different from the brown. It is throughout the eggshell rather than mostly on the surface as the brown is. It comes from a different source (liver) and gets deposited at the same time as the calcium carbonate that makes up the bulk of the shell material. " [Lee Sellers, 1st quote from Poultry Genetics for the Non-Professional website and the 2nd from a different forum.]

 

[keystonepaul]

Some of it was off of this website:
[URL]http://www.utilitypoultry.co.uk/eggcolour.shtmlI looked at som many places while looking at egg color in general. It was thought that the limiting factor in blue egg production was the production of the "stuff" (there's a tech term huh) that makes the egg blue and that the blue is throughtout the shell, not just the outer layer. The reason behind smaller eggs was never clear whereever I found it. They kinda hinted that eggs would be smaller over time as an adjustement to the limited blue pigment but increased need to produce an egg. Soo if you selected for egg production (breed hens that were your better producer numbers wise) wanting more blue eggs you might be selecting for smaller eggs as a result and perhaps a lighter shade of blue in addition. Keystonepaul

 

[McSpin]

From what I can determine, this is a hypothesis, not fact. Often times, small size and decreased fecundity comes from selecting only for one or two traits and ignoring important ones, like size and production. If you want large blue eggs, you have to select for both. The same with blue and high production. I would bet you could make good progress with the right breeding program.

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[tadkerson]

The group has done a pretty good job of explaining things.

The blue egg pigments ( biliverdin-IX, zinc biliverdin chelate, and protoporphyrin-IX) are produced from a substance called biliverdin. The body (different places) breaks down old worn out red blood cells and uses the hemoproteins in the red blood cells to make biliruben and biliverdin.

In chickens the hemoproteins (from broken down blood cells) are collected by the shell gland from the blood and converted to biliverdin which then can be used to make the blue pigments that are added into the shell.

I worked with blue egg shell color for 6 years. I believe that the amount of blue pigment a bird can add to a shell is limited by 1. the number of red blood cells the chicken is recycling, 2. the efficiency of the birds body to convert blood cells to specific kinds of proteins, 3. the size of the egg, 4. the number of eggs laid by the bird. ( smaller eggs and fewer eggs/week make for a darker egg shell).

Tim

 

[Sonoran Silkies]

That seems to be pretty much what Sellers found--and he bred for blue eggs and production for a long time.