You feel the changes, your ears grow longer, as does your body. You collapse onto your hands, or hooves now, as your body elongates and grows a fleshy tail. Your face grows longer. Suddenly hair starts to sprout over your skin, and it turns iron grey. You are now a donkey. You find that you are a female donkey, you have grown a pussy that has moved between your back legs, and your normally muscular chest has filled out to become enormous breasts. The centaur snorts and starts caressing you, playing with your hair, rubbing his hot cock along your back. It squirts some more pre-cum that spreads all over your back, dripping off your tail and sides. Without a warning he mounts you, and shoves his huge cock into you. You give a squeal in surprise, as he starts pumping in and out of you, your pussy is being stretched enormously. His forlegs grip your sides, you are rocking back and forwards as he thrusts violently into you. His human hands are gripping your neck, pushing you backwards into him so he can bury further into your vaginal walls. You moan in pleasure and start pushing yourself back into him, making his hot, sticky cock bury deeper and deeper inside you. His balls start to slap your ass, your body is experiencing a wonderful sense of pleasure as he shoves his cock all the way into you. You start to tremble...and suddenly he cums, and you orgasm, moaning tensing. You both collapse onto the ground, his MASSIVE cock still stuck inside you as your pussy tightens up. White cum starts leaking out of you, covering your ass in his juices. The centaur is breathing heavily, he is trembling now, and you feel his cock go limp, no longer hard, and fall out of your pussy. You get up and touch his cock. He shivers in delight. You put it in your mouth and swallow all the remaining cum. You lick up it, until you reach his balls. You start to suck on them hard, and he moans in pleasure. With your hands, you move them up and down his huge cock slowly, then faster until you are masturbating him. His cock hardens again, and you shove it in your asshole. You groan as a mixture of horror and delight overcomes you, and you shove his cock in further, starting to work it in and out of your hole. He cums again, and you (again) both experience a blissful experience. You lie next to him, between his legs, his cock still stuck fast in your ass.