The Messenger of Allah ﷺ forbade the flesh of domestic asses on the day of Khaibar, but permitted horse flesh. (Using translation from Abū Dāʾūd 3788)
نَهَى رَسُولُ اللهِ ﷺ عَنْ لُحُومِ الْحُمُرِ قَالَ سُرَيْجٌ الْأَهْلِيَّةُ يَوْمَ خَيْبَرَ وَأَذِنَ فِي لُحُومِ الْخَيْلِ