In his dream, Ty saw a handsome man stood over him, a few years older than he was. Ty was transfixed by his handsome, muscular body, his firm arms and legs and the seven inch shaft between his legs. Ty sat up, guided by the man, and put his mouth around that hard cock, sucking it eagerly, feeling the man's hips thrust against his face faster and faster, his own body aching for the warm seed to feed him...
He sat up with a start, his body feeling hot and his horniness from the dream still present in real life. Why had he dreamed about a man fucking him? It made no sense! He was a breeder slave, meant to impregnate women for the beasts, wasn't he?
But his body told him a different story. He felt an aching, empty feeling in his loins, and he suddenly realized it hadn't just felt like he'd cum all his seed inside that girl- he really had. His brain was fixated on the cock from his dream, and fantasies about it being inside him filled his mind.
Before his eyes, his length was starting to dwindle, and it felt so good how the nerve endings were concentrating around a rapidly tinier point. His body in general was slimmer and less muscular, his figure more curvaceous, and he had barely noticed, being distracted by the changes to his penis.
The changes were accelerating, though. His emptied balls moved up inside him, reshaping into ovaries, and his scrotum tucked inwards beneath his still shrinking penis, a slot opening along it made to take things inside it and fill the empty feeling he felt- the need to be bred.
As his penis continued to tug back into him, his chest rapidly changed. His nipples swelled and increased in sensitiveness tenfold, and when he rubbed them he moaned in his new, higher voice. Flesh built up around them, and she ached with anticipation at the thought of a man firmly grabbing her chest, pulling and pinching and sucking and biting her nipples.
She realized, she wasn't thinking of herself as a boy, she was a girl now. Her old penis had finished receding into a sensitive clit, and her body was ready to be bred as soon as a man came to fuck her up.