Sayyiduna al-Bara (may Allah be pleased with him) says that the Messenger of Allah (peace and blessings be upon him) ordered "that the meat of domestic donkeys, raw and cooked, be thrown away," and after that he did not give permission to eat it.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الضحايا / 19457