Za'idah said: I said to Khusayf: Did Abu Ubaydah bin Abdullah bin Mas'ud narrate to you from his father that he said: "For twenty-five camels, a one-year-old she-camel (bint makhad) is due; if there is none, then a two-year-old male camel (ibn labun)"? He said: Yes.
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 9555