If you in breed or line you can get plenty of subfamilies of said strain as well as letting a trustworthy buddy breed a yard of the fowl as well. Never let a none vigorous or otherwise second rate fowl from such a family breed or it will be carried on and that's going to be difficult to breed out or nearly impossible.
From all that I've read it's possible to have such for 20 years, but eventually you need to cross to another pure strain bred for years very similar in all ways to your own strain but test to make 100% of such before cross you wouldn't want to cross with inferior birds after you've spent so much time,heart and soul in your own birds.
From all that I've read it's possible to have such for 20 years, but eventually you need to cross to another pure strain bred for years very similar in all ways to your own strain but test to make 100% of such before cross you wouldn't want to cross with inferior birds after you've spent so much time,heart and soul in your own birds.