And sometimes the animals look all right, but their purity is questionable. They then have to be interbred, and any of their offspring that are too far off the mark have to weeded out in the process.
也有的看來很像，但血統「純度」可疑，這時就須以親兄妹交配、淘汰模樣差太多的下一代方式，進行「純化」。