Test Mating for O/O

Once I find a suitable Blk or Blue Ameraucana rooster (fingers crossed), I’d like to test mate him against ((insert good candidate here)) to make sure he carries two copies of the blue egg gene. This is a must. In theory if he is O/O, all his offspring will inherit a copy and the daughters will lay a blue-shelled egg. But if he only carries a single copy, then half the daughters will inherit and half won’t….and I’ll know I need to find a different rooster.

So I’m thinking a white egg layer would work best. Maybe a Leghorn? That way I could keep a few daughters as layers for myself, or sell them for cheap as backyard laying crosses. Or I suppose I could use Lily (my BR hen) and create sex-links, which would be a plus in itself as long as egg colour wasn’t too compromised. I need to be able to tell at a glance who is laying what. Opinions? Am I missing anything?

TIA!

Unfortunately I don`t think it is as easy as that. Egg colour has a lot of modifiers when you start to deal with brown. That is why there can be so many aqua to olive green coloured eggs.
I have only dabbled in this a bit so someone else may pipe up (hopefully) and give a bit more information.
It is a long road you are going to travel as when you choose the hen to mate him to you have to hatch LOTS of eggs and then grow the pullets out to laying age. Then you have to have them all separate so you know for sure the egg colour they are laying. I would think you would want 50-100 pullets to know for sure.
Most people when crossing use a white layer as this will only dilute the blue and make it a bit paler, where brown gets laid over the blue and makes it a shade of green.
Back when I was playing with this a bit, I would just use a very good quality rooster, only hatch the best colour eggs, and keep a cockerel from the best coloured eggs to use for the next year. If you keep track of what egg the cockerels hatch out of that is the best way to make the best headway. This works for the dark brown eggs as well. Always keep a cockerel from you darkest brown eggs and you will improve egg colour very quickly (I have more experience with that than the blue).
I am interested to hear how your project goes. Egg colour has always really interested me.

If all you want to know is whether he's carrying two Os, any hen that doesn't lay blue or green eggs will work.
If he has two O's then all daughters will lay blue or green eggs (depending on whether you cross him to a while or a brown egg layer). If he has only one O, then half his daughter will lay blue or green eggs (same "depending" as above). You'll need to hatch out quite a few to be sure.

If he is in fact carrying only one O, then the probability that n daughters will all lay blue/green eggs is 1/2 raised to the power n - e.g. for 2 daughters, it's 1/4, for four, it's 1/16. If you hatch, out say, 10 girls and they all lay blue green eggs, you can be 99.9% sure he has two Os.

Coopslave: As my grandmother was overly fond of saying, nothing worthwhile is ever easy! Ok, I’m probably going to go with a white layer (probably a couple Leghorns, variety dependant upon availability) because it would be simpler than dealing with brown egg genetics when there is really no reason to go there. Now hold up. 50 to 100 chicks seems like an awful lot for a test mating! Wow... I could possibly do 25, and hope half turn out to be pullets, give or take a few. Otherwise, I will have to wait until next summer/fall because I don’t have the required space as of yet. Sigh…it appears I’m getting ahead of myself once again. I should probably just wait until after the move, but oh it is hard. So much to do, so little room. LoL I’d love to get ahead start though. And from now on I will be selecting only the bluest eggs for hatching, as I’d really like to improve on colour. Keeping track of what shade of egg hatched what cockerel sounds like a great way (dare I say short cut?) to making faster progress. Clever! Looks like I will be getting chick leg bands after all. Thank you for your input. Egg colour fascinates me too.


Ipf: Yes, this test would be all about confirming O/O or O/o. I really think a white layer would suit my purpose better. Also, if I use Leghorn hens the daughters would be decent enough layers (hopefully) I shouldn’t have any trouble selling them, even as crosses. The sons would be culled (likely to the freezer) as soon as maleness was confirmed. And just so I’m clear, what you’re saying is I wouldn’t need to hatch out quite so many chicks to confirm the rooster is homozygous for blue eggs, though the more I hatch out the truer the test results will be?

eta: Nevermind that last part. I reread what you wrote and understand - it helps when one doesn't have a hungry rugrat hanging off them. LoL Thank you much.

It does sound like you will not have to hatch as many as I though. It was just a guess on my part. That must be good news!
I look forward to hearing how it goes.

You can't ever be absolutely certain, but a 1 in 1000 chance of being wrong is pretty close. (You can do the math for yourself, or even look it up in any basic stats text; I certainly won't take offense if you don't want to take my word for it).Of course, if you hatch ten daughters and even one of them lays a non-blue/green egg, they your guy is O/o.

There is a certain charm in those green eggs; I have a couple of girls who lay dark olive green, and people love them. But I take your point about the productivity of the leghorns.

Interestingly, leghorns are said to carry a sex-linked egg shell colour inhibitor, so the cross might not work the other way around (leghorn roo x Amer hen), as all would lay white. However I don't know if it inhibits all egg shell colour or just brown, since that is a different biochemical pathway.

Oh these genetic things are just so interesting, I love to listen. have a wonderful and great day, CynthiaM.

^^ It sure is! I will definitely update when I have something new or exciting to report.

Very true. 1 in 1000 is good enough for me. lol Interesting about the Leghorn cross reversed. And I’m with you there ipf. Green eggs can be as pretty as blue. My silver EE hen lays a pretty olive egg, though it’s not very dark. Someday I’d love to have chickens that produce a grass-green egg shell, but that’s a whole other project. (Barred, bearded, muffed EE’s come to mind )