I say, and with Allah's success: There is no zakat on mules and donkeys unless they are for trade, in which case they are subject to the zakat of goods; as narrated by Abd al-Rahman ibn Samura, he said: "There is no charity on the mule, the donkey, and the donkey's offspring" in Sunan al-Bayhaqi al-Kabir 4: 118. And from Abu Huraira, he said: "I have excused you from the charity on the donkey and the mule and the donkey's offspring" in Sunan al-Bayhaqi al-Kabir 4: 118. The term 'jabhah' refers to horses, 'nakhah' refers to slaves, and it is said that 'kuskah' refers to working cattle, and Allah knows best.