you can line breed animals indefinetly to suit their environment(work), just as long as you are honest about the quality of the offspring , and you are matching best to best of the related offspring. you people that are breeding dogs for shows can not maintain healthy dogs , because you dont make the dog earn its keep and prove its genes in the real world. just as all animals are in the wild they are basicaly like clones of each other and perfectly adapted. this is the only way to actually get a breed.