changing roosters

[TomCircle]

How long will it take after removing roosters from flock for the fertilized eggs held in the chicken to "wear out" before I can put in a new rooster for accurate blood line breeding? I have about 7 different roosters that will be taken to a local processor, but want to order the same breed roo as my new hens to breed that particular stock, to keep the breed self sustaining. Any thoughts?
Thanks, Tom...

 

[RedDrgn]

I believe the rule of thumbs is 30 days to be sure your hens are fertilized by a new roo and not the old.