Anas bin Malik (may Allah be pleased with him) narrates that a man from the tribe of Kilab asked the Prophet (peace and blessings of Allah be upon him) about taking a fee for letting a male animal mate with a female. The Prophet forbade him from doing so. Then the man said: "O Messenger of Allah! We let the male mate with the female and we are given a gift (in return), so what is the ruling on that?" The Prophet permitted him to accept the gift.

Imam Tirmidhi says:
This hadith is Hasan Gharib. We know it only from the narration of Ibrahim bin Humaid, who narrated it from Hisham bin Urwah.