Yahya related to me from Malik from Nafi that Abdullah ibn Umar
used to say, "If a she-camel that is being driven as a sacrificial
animal gives birth, the offspring should be carried along as well and
they are sacrificed together with her, and if there is no place where
they can be carried, they should be carried on the mother until they
are all sacrificed."
Muwatta Malik Book 20, Hadith 147