Breeding chickens?

[Cason]

I couldn't find a breeding topic, so if this post should be moved, please.. do so!

I have a Delaware rooster and a Delaware hen. However, I also plan to have a Light Brahma rooster in the hen coop (there are 19 hens)
If I wanted to breed for pure Delawares, how long should I isolate that pair for "pure" egg gathering for my incubator?

 

[Cuban Longtails]

approximately 3 - 4 weeks.

 

[hinkjc]

I separate mine for a full month before collecting eggs to ensure they are fertile from the correct rooster.

Jody