Thank you, you've been very helpful!!A general rule for close line breeding is about 8 generations. But there are other factors to consider, like how closely related foundation stock is, and how many unrelated hens you start with. A line developed from a single hen and rooster won't be able to withstand line breeding as well as a line founded by 6 different hens and an unrelated rooster. The more genetic diversity you have in your foundation birds, the longer you can 'safely' line breed before you start encountering serious issues.