The mare whinnied at Ed, her nostrils flared as she triedto figure out the confusing scents coming from Ed. The boy's eyes were glazed as he stripped off the rest of his clothes, past caring if anyone saw him naked. He stood there, breathing in her sweat-scent, feeling his horsecock swell. But something else seemed different, too.
He looked down at himself and realized that his whole body was larger, with a little hair pushing out of his chest. Amazed, he went over to a water bucket and looked at his reflection. His face looked different - harder, more defined. He blinked and reached up to feel what should have been smooth cheeks, and encoutnered stubble.
Instead of fourteen, he looked to be closer to twenty! A horse-hung, muscular super-stud twenty. Instead of being scared, the chnges only fired up his lust even higher, and he turned back to the mare. She was squatting slightly, her head bent low in submission, and her cunt was dripping. Ed stumbled slightly as he moved behind her, his horsecock now erect and getting even larger. She didn't look so big now - if he'd been able to think clearly, he might have looked down to see his legs lengthening and changing into horse's legs. And he might have been concerned that he was now a very beefy 25.
He almost fell over her rump, and had to thrust several times before his swollen flare penetrated the thick black lips. Shifting position, he was able to push deeper as his body continued to adapt and change.
He slid over her back now, lost in an orgasmic haze as his body gained mass and size, arms lengthening and changing into forelegs as his face pushed out into a muzzle. All he could think about was mating, his mind overrun by the instincts and desires of a mature Percheron stallion. Which was just as well, for by the time he shuddered in release, that was exactly what Ed was.