As you moved back towards Jessie a scent hit your nostrils. It was a wonderful, arousing smell as you moved back behind her, not noticing as you fell onto all fours, your transformation now accelerating as your new horse cock slid into view, still growing larger as it did. The mare unconsciously pushed her tail to the side to reveal her aroused vagina that winked at you and you took a sniff.
Instinctively you knew that this mare was in heat, your instincts told you to mate with this mare and take her as your own. You wobbled a little on four legs before you ran your tongue slowly along her teats and vagina causing her to whinny. For a moment you had a flash of a human woman, but that didn't make sense, you weren't human, were you?
Jessie stared back at the stallion, despite not wanting to be mated her new horse body was reacting to the stallion's presence. She could feel the heat growing in her loins and was having a hard time resisting. she whinnied again as she felt the stallion's tongue enter her, but what she really wanted was that cock of his. The very idea of it piercing her new equine body excited her, she wanted him to fill her with his seed and impregnate her with his foal.
She wanted... no, she needed this more than anything right now! Despite her human side's protests, she raised her tail again as the stallion backed up, she wasn't about to let him get away from her.
You finally couldn't hold back anymore as you reared up onto your hind legs and fell onto the mare's back. It took some experimental thrusts before she finally neighed loudly as you penetrated her vagina. You thrust faster and deeper into her, the two of you giving fully into your animal instincts as you thrust faster and deeper into her. The tight depths of her body felt so good as you prepared to breed her, she was your mare, and she'd bear your foals.
For a brief moment you thought that maybe this was wrong, but why would it be? You were both horses, after all, you pushed those thoughts out of your mind as you thrust faster and harder into her. You bit down on her ear as she whinnied loudly s you thrust down to your hilt. Your balls slapped against the beautiful white and yellow mare's backside as you did, it felt so good you didn't even notice as your transformation completed and your fate was all but sealed.
Now as far as you were concerned, you were always a stallion as you thrust in one last time and your balls churned as your cum spurted out of your shaft's head and painted the walls of her vagina white as you both neighed loudly. She clamped down on your cock and drew out all of your cum into her womb, the mare in her was now happy.
You pulled out of her, now a horse in mind and body as you started to graze.
Jessie's mind started to come back into focus as she felt the combined juices drip down her hind legs. Her human side was distressed, she was now nothing more than a broodmare and probably pregnant by the stud who used to be her boyfriend. This wasn't what she had in mind when she wanted them to someday start a family.
She sighed inwardly and started grazing next to him. If she wasn't going to be human anymore, at least she could be close to her boyfriend, even if he didn't remember her.