وَقَالَ أَبُو يُوسُفَ: تَجِبُ فِيهَا وَاحِدَةٌ مِنْهَا
Translation: Abu Yusuf said: One of those very animals is due from them.
In his view, an all-young qualifying herd is not automatically exempt: a young animal from that category may be given. Abu Hanifah and Muhammad apply the stipulated maturity of the due animal in a way that does not make an exclusively juvenile herd sufficient.