You moved behind Jessica who was starting to graze as if she hadn't just been a human a few minutes ago. You pressed your muzzle up against her flanks, getting a good sniff of her pheromones. She let out a whinny as she glanced back at you, her vagina winking at you as if she readied herself.
You felt your shaft poking out of its sheath. You weren't human anymore and probably weren't going to be human ever again, so you might as well enjoy yourself. You raised yourself on your hind legs and came down on her back, causing her to neigh as she felt your weight on her. You thrust experimentally for a few seconds as your large horse shaft rubbed against her legs and teats before you finally felt it pressed against her vagina.
She let out a whinny as you thrust into her, taking her like the animal you had become. Your horse instincts were overtaking your human mind, but you didn't really care. All you cared about was getting revenge on that bitch and this was the best chance you had right now as you thrust in and out of her, biting down on her ear a little as she neighed louder.
There was nothing left of the woman you once loved, all that was left was this broodmare. You no longer cared, all you cared about was making her your mare. You thrust in and out of her harder, her equine vaginal muscles constricting around your massive shaft as she whinnied with pleasure.
You could feel your balls slapping against her flanks as you bottomed out in her. You could feel your humanity slipping away as you filled the mare with your stallion meat. You could remember being human, but you perceived yourself more as a horse now. You only thought about taking her and filling her with your seed to impregnate her now.
You both shared a loud neigh as your balls churned before painting her insides with your cum. YOu felt her vaginal walls clamping down on your shaft as it drew out more seed.You breathed heavily as you slowly started to pull out, your shaft pulling out with a pop as your cum started to drip out of her vagina.
You looked back at Carla as your human memory started to reassert itself. Now you were the perfect mix of human and horse. You were smart enough to think for yourself, but you wanted to mate with this mare and others.