Murray McMurray Cuckoo Marans genetics questions

[Aziara]

I've been goofing around with the Chicken Calculator, and I think I might have a crossbreeding gameplan. But, I want to know more about the genetics of the birds involved first.

For example, the Cuckoo Marans from Murray McMurray, what is the 'extension of black'? 4 options on the calculator show black/white barring: E/E, E/e, E/E^R, E/e^b.

Any of these would work for what I want (which is possibly making the Bielefelder smaller/more heat tolerant by hybridizing with the smaller Marans, while being able to breed back to autosexing), but some of those genetics can have the option of possibly creating a silver line too.... which is quite interesting.

And second question: Would a silver duckwing barred also be autosexed like the gold duckwing barred?

 

[NatJ]

I've been goofing around with the Chicken Calculator, and I think I might have a crossbreeding gameplan. But, I want to know more about the genetics of the birds involved first.

For example, the Cuckoo Marans from Murray McMurray, what is the 'extension of black'? 4 options on the calculator show black/white barring: E/E, E/e, E/E^R, E/e^b.

They are supposed to be E/E, but in practice it could be any of the things you listed, and they would still look black (with the white barring.)

If you breed to something else, and you get chicks that are not black-based, you will know that the parents are not pure E/E.

Most likely, you will get black chicks (from E/E Marans parents), and then breed them back to Bielefelders to get 50% that show the wild-type pattern and 50% that show black (both with the white barring, of course.)

Any of these would work for what I want (which is possibly making the Bielefelder smaller/more heat tolerant by hybridizing with the smaller Marans, while being able to breed back to autosexing), but some of those genetics can have the option of possibly creating a silver line too.... which is quite interesting.

Whether it's E/E or E/_?_ will not tell anything about whether they have gold vs silver.
Many barred or cuckoo birds do have silver, so yes you have a fair chance of getting some silvers in future generations.

Silver is on the Z sex chromosome, just like barring is, so it cannot pass directly from mother to daughter. So if you want to avoid silver, just cross a Bielefelder rooster (gold) with Marans hens, and keep only daughters, who are certain to have s+/- (gold on their only Z chromosome.)

If you do want Silver, you can do the first cross either way and keep only sons, then breed those males to Bielefelder hens and look for silver among the not-black chicks. Or you can cross a Marans rooster to Bielefelder hens and keep daughters, then cross to a Bielefelder rooster and look for silvers among their not-black sons.

And second question: Would a silver duckwing barred also be autosexed like the gold duckwing barred?

Probably yes, although I haven't seen them to be sure.