"Jessie here is one of our newest mares, and she's already in heat," the attendant said as Jessie let out a soft whinny. "She joined not long before you did, and this is her first heat. I think she'd be a fine first mate for you my handsome stud."
You got up, already used to standing on four legs you could feel the arousal growing as Jessie did the same. Caroline let out a whinny of protest as the attendant smiled and looked at her.
"Don't worry Caroline, you'll get your turn soon enough," the attendant said with a smile as Maria stirred from her stall and looked up. The attendant lead you out of the stall and opened Jessie's stall where the Arabian mare was already turned away from you, her tail pushed to the side to expose her winking vagina to you.
Your arousal was too much, your erection was almost painful at this point. You wanted to mount that mare and take her as your mate as the horse side was pressing at you to do so. Your human mind protested, saying that it was wrong and you were in love with Jessica anyway, it felt like you were cheating on her.
But the horse side was winning, maybe it was because you were in a horse body, maybe it was the arousal, maybe you really wanted this deep down. You finally couldn't hold back any more and mounted the mare, putting your full weight on her as you pressed the flared tip of your horse cock against her slit.
There wasn't any more hesitation, the mare whinnied loudly as you thrust deep into her. You couldn't stop yourself as you began to thrust in and out of the mare, and you didn't care. The sensation was amazing, it was so much better than sex with Maria because you felt fully in control this time.
You thrusted in and out of Jessie as you pressed in deeper, you could feel your balls swinging back and forth as you enjoyed the sensations of mating with this mare. You wanted to do this more, you wanted to take as many mares as you could as your own, converting more humans into horses as well.
You let out a neigh as you thrusted in as deep as you could, feeling the sensation of sweaty and wet fur rubbing against each other as your balls slapped against her. You whinnied loudly as you felt her vaginal muscles clamping down on you and you came hard into the mare, her muscles drawing it out as you both whinnied in unison, your seed filling the mare.
As you felt utterly spent you pulled out and bowed your head a little. You didn't feel any guilt, you were an animal even if you remembered your human side, and you enjoyed every moment. If you weren't ever going to be human again, you might as well enjoy your new life.
"Good boy," the attendant said as she took you and lead you back into your stall before smiling back at Jessie. "Excellent work, we had some trouble getting her with the stallion that turned her earlier. I guess it took a special connection and the heat to finally get her to give in, now you're both like this forever. You still make a cute couple though, a shame it won't be just the two of you anymore."
You looked at Jessie's stall again as she finally was able to drift off to sleep. That had been Jessica? Now everything was starting to make sense, but at least you hadn't completely lost her.
You closed your eyes and finally drifted off to sleep.