There is only one breed of chicken, the red jungle fowl otherwise known as Gauls Gauls Domesticus. All other strains of chickens for better or for worse are inventions of mankind. This means that the proper DNA is already on hand if for any reason mankind needs to or ever wishes to resurrect one of these endangered strains or breeds from the grave. For whatever it is worth duel purpose chickens are breeds or strains of chickens that are unable to do anything well. In other words they are neither fish nor fowl. However the ones that you rescue belong to you and to you alone so by all means knock yourself out.
Now if I may. If you are planning on rescuing one of these breeds that breed should be the only breed that is permitted on your place. I have seen way too many accidents happen when the chicken keeper turns his back for just a second and a strange rooster runs into the brood pen to deposit a cargo of non-standard DNA. Also with the shallow gene pool that you'll be dealing with, strenuous culling must be practiced in order to succeed.
Now if I may. If you are planning on rescuing one of these breeds that breed should be the only breed that is permitted on your place. I have seen way too many accidents happen when the chicken keeper turns his back for just a second and a strange rooster runs into the brood pen to deposit a cargo of non-standard DNA. Also with the shallow gene pool that you'll be dealing with, strenuous culling must be practiced in order to succeed.