Changing Roosters.

[easyjet23]

I purchased some Black Star and Barred Rock Hens about 2 weeks ago. They were running with a Barred Rock rooster. They are now running with my Black Sumatra rooster. How long will it take for my hens to start laying my roosters fertilized eggs? Any help will be appreciated!

 

[ChickenCanoe]

I believe it's 2 weeks but I'd like to know for sure since I'll be swapping roosters several times this fall.