"You see, Miss Willowsworth, your incredible speed and endurance are traits that I can't help but admire. And as a scientist, I can't resist the opportunity to study them, enhance them, and apply them to other... species." Dr Eliza explained with a wicked smile, examining Abigail's body as she waited for her serum to take effect.
Dr Eliza didn't have to wait long, as Abigail felt her ass start to swell, the muscles in her cheeks slowly stretching and growing, pushing outward as if inflated. "Wh... wha... what the fuck did you just do to me!?" She stuttered, her voice trembling with fear.
Dr Eliza's eyes gleamed with excitement as she watched the transformation progressing, fine hairs starting to sprout from Abigail's thighs. "You see, Miss Willowsworth, I've developed a serum that combines your extraordinary human genetics with those of a thoroughbred racehorse" Abigail's eyes bulged in shock, barely able to process what she had just heard.
As Dr Eliza continued her explanation Abigail stuggled against her restraints with renewed vigour, trying not to focus on the growing heat in her crotch or the fact that she was losing sensation in her hands and feet. "My goal is to create the ultimate equine specimen, one that can outrun any horse ever bred in the natural way." continued Dr Eliza.
"Bred?!!!" Abigail finally managed to scream, her eyes filled with abject horror. With a sick grin Dr Eliza responded, "Yes, bred Miss Willowsworth, you're going to make a fine breeding mare".