Reference for Chullin 170:17

שחיטת אמו מטהרתו תהני ליה שחיטת אמו ולא ליבעי שחיטה קמ"ל

Now since the Rabbis hold that the slaughtering of its dam renders it permitted, then [in this case, too, where the dam was a trefah I would say that] the slaughtering of the dam should serve for it too and it should not require slaughtering; he therefore teaches us [that it is not so].'

Jastrow

Jastrow