Thuwayr narrates from a shaykh of the people of Quba, who narrates from his father, who was a Companion of the Messenger (may Allah be pleased with him), that he asked the Prophet (peace and blessings be upon him) about drinking the milk of she-donkeys. He (peace and blessings be upon him) said: "There is no harm in it."
This report is not strong.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الضحايا / 19675