Making blue eggs bluer

[Willawong Hill]

So that was what I was asking, was how can you tell that either parent carries two copies of the blue egg gene? I’m not sure that you can

I think what you have to do is cross the blue egg layer with a white egg layer. If all pullet offspring lay blue eggs then your blue egg layer is probably homozygous; however, if even one pullet lays white eggs then your blue egg layer is heterozygous. Problem is you end up with a lot of pullets you know are heterozygous then so only useful to try if you have time and space.

 

[OhZark Biddies]

I think what you have to do is cross the blue egg layer with a white egg layer. If all pullet offspring lay blue eggs then your blue egg layer is probably homozygous; however, if even one pullet lays white eggs then your blue egg layer is heterozygous. Problem is you end up with a lot of pullets you know are heterozygous then so only useful to try if you have time and space.

Right, so by getting a white egg laying pullet from your cross, you can know that the blue layer parent is heterozygous for blue eggs...

but even if you hatch 1000 eggs and all result in blue egg laying pullets, you still can’t truly know the blue egg parent is homozygous, the best you can do is assume that it most likely is.

That was my point, I’m not sure you can truly know. Unless I’m still missing something.

 

[Willawong Hill]

I guess you just rely on probability, if you have 6 blue egg laying pullets the probability that the blue egg laying parent is not homozygous is only 1.5%, if you have 1000 then it's 1 in 2 to the power of 1000 (an infinitesimally small number), not zero I suppose but close enough for me. Eventually DNA will get good enough that they will be able to check for individual genes. For example in horses you can check if they are homozygous for certain coat colours such as black by sending off hair samples.

 

[OhZark Biddies]

Right so at best, on paper we can assume it is likely, but we can not truly know it to be true....

but even on paper, if we do test matings with large hatches and grow out all the resulting pullets and confirm all of their egg colors, there is a very strong chance that individuals needed to confirm a parent is heterozygous might be one of the unhatched eggs or one of the approximately 50% that are cockerels...

and from a statistical point of view this immediately invalidates the probability numbers, because you simply can not confirm anything in over 50% of the resulting offspring, at least not without some sort of exponential test mating of all of those males...

but the reality is most hobby chicken keepers and even most serious breeders are not going to do significantly large hatches where they keep all the resulting pullets for the time needed to confirm egg color...

and of the smaller hatches done since roughly half are going to be males which gives us no way to confirm anything about half the hatch, we’re still left guessing...

and then even with the resulting females, the chicken keeper must wait 5-6 months minimum or so to know what the resulting egg colors are...

Which leaves us with the conclusion that very, very few people at all would really know if they have birds that are homozygous for the blue egg gene.

Which all makes me question the idea that homozygous for the blue egg gene creates a better/darker blue, I just don’t see how this can be known to be true by most of the people that make that statement ( I’m not saying anyone on this discussion has said that, it’s just something I’ve seen repeated a lot in general)...

And I’ve read discussions among serious Ameraucana breeders on that breed’s forum, that they produce birds that throw a white egg after generations of work on improving blue egg lines, which has made them question the conventional ideas about it all as well.

Which is why I was asking originally how anyone can tell that either parent carries two copies of the blue egg gene? I don’t think anyone really can.

 

[NatJ]

Which is why I was asking originally how anyone can tell that either parent carries two copies of the blue egg gene? I don’t think anyone really can.

As a practical matter, test mating can make someone pretty sure. Not absolutely sure, but pretty close.

And test mating can certainly identify a lot of heterozygotes, so they can be removed from the breeding pool. It just cannot be certain of identifying every heterozygote.

You're right that test mating takes a lot of time and space, to raise enough pullets to laying age, so it's often not practical.

When making Easter Eggers, people often take a shortcut by using the pea comb gene: it's linked closely enough to the blue egg gene to be a useful marker. Of course the linkage can be any direction: pea/blue like Ameraucana, not-pea/blue like Cream Legbar, pea/not-blue like Brahma, not-pea/not-blue like Orpington. And crossovers happen, so you get a few right-comb/wrong-egg birds in any flock that is being selected that way.

 

[OhZark Biddies]

As a practical matter, test mating can make someone pretty sure. Not absolutely sure, but pretty close.

And test mating can certainly identify a lot of heterozygotes, so they can be removed from the breeding pool. It just cannot be certain of identifying every heterozygote.

You're right that test mating takes a lot of time and space, to raise enough pullets to laying age, so it's often not practical.

When making Easter Eggers, people often take a shortcut by using the pea comb gene: it's linked closely enough to the blue egg gene to be a useful marker. Of course the linkage can be any direction: pea/blue like Ameraucana, not-pea/blue like Cream Legbar, pea/not-blue like Brahma, not-pea/not-blue like Orpington. And crossovers happen, so you get a few right-comb/wrong-egg birds in any flock that is being selected that way.

I doubt many people really do test mating for egg color, but maybe?

test mating for feather color makes a lot of sense, but for egg color it seems unlikely to do much more than confirm heterozygous individuals or rule out nullizygous individuals...

I’m just not seeing it practical, beyond theory, for “knowing” anything about homozygous for blue egg color.

My interest in it all, just comes from trying to find something documented on the idea that homozygous for blue egg color creates better blues... I cannot find anything credible on that.... just somewhat random statements on blogs or on BYC... but nothing from serious breeders or researchers ... but maybe I’ve missed it.

 

[NatJ]

My interest in it all, just comes from trying to find something documented on the idea that homozygous for blue egg color creates better blues... I cannot find anything credible on that.... just somewhat random statements on blogs or on BYC... but nothing from serious breeders or researchers ... but maybe I’ve missed it.

I haven't seen anything credible about that either, and I'm a bit skeptical. My guess would be that some modifiers make the difference, and that producing birds homozygous for blue color also produces birds with more of the right modifiers.

I doubt many people really do test mating for egg color, but maybe?

test mating for feather color makes a lot of sense, but for egg color it seems unlikely to do much more than confirm heterozygous individuals or rule out nullizygous individuals...

I don't know how many people do it, but it's always seemed logical to me
If you once get your breeding stock homozygous for the trait, you no longer have to think about selecting for it.