It was narrated that Qatadah said:

I heard Jurayy bin Kulaib say: I heard ‘Ali (رضي الله عنه) say: The Messenger of Allah (ﷺ) forbade (sacrificing) an animal that had lost most of its horn or ear. Qatadah said: I asked Sa`eed bin Al-Musayyab: What does lost most of its ear mean? He said: If it has lost half or more of it.

حَدَّثَنَا حَجَّاجٌ، حَدَّثَنِي شُعْبَةُ، عَنْ قَتَادَةَ، قَالَ سَمِعْتُ جُرَيَّ بْنَ كُلَيْبٍ، يَقُولُ سَمِعْتُ عَلِيًّا، رَضِيَ اللَّهُ عَنْهُ يَقُولُ نَهَى رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ عَنْ عَضَبِ الْقَرْنِ وَالْأُذُنِ قَالَ قَتَادَةُ فَسَأَلْتُ سَعِيدَ بْنَ الْمُسَيَّبِ قَالَ قُلْتُ مَا عَضَبُ الْأُذُنِ فَقَالَ إِذَا كَانَ النِّصْفَ أَوْ أَكْثَرَ مِنْ ذَلِكَ‏.‏