As you you start stroking your masssive dick, it starts to harden and grow enormous. The pleasure you get is so intense that you don't notice the changes in your body have started again. You writh in pleasure as you rub your now enormous hard dick not seeing that your body is becoming hairier. Your mind is filled with strange images of Jennies! You become more and more excited about the thought of putting your huge dick inside another donkey! With your eyes now closed, relishing fucking a donkey you don`t see your legs becoming less human and your toes fusing into a hard solid hooves and your face pushing out. You finally climax and shout out a loud HEEE HAAAW.
The loud bray makes you open your eyes and with shock you see your self in the mirror. You are now almost a complete donkey, still on two legs but only just. As you let go of your dick the final changes take place. Your fingers fuse and darken and turn into hooves, your teeth and tongue grow larger as your eyes move to the side of your head and your head is that of a full donkey, your neck lengthens and as it does you fall on all fours. Your arms get bigger and hairy to match your back legs, they are now fully formed front legs. The changes slowly subside and you bring your head up to look at yourself. You see a complete and fully formed Jack donkey. But you are not upset at what you see, in fact you now realise it is what you have always wanted, to be a donkey. You open your mouth and let out a satisfied HEEE HAAW and you mind turns to pastures and jennies.