Horse Cock Breeding Serum

Woman hugging the head of a white horse.
The book cover of "Horse Cock Breeding Serum" written by erotica author Thomas Pike.

Julie and her mother are in a race against the clock to find a solution to the dwindling horse population. The older woman cooks up a serum that her daughter gladly tries out. As her body heats up and her jeans grow tight, Julie is shocked when a massive horse cock explodes out of her pants. She can't wait to use it to breed every mare in sight, hoping it's the answer to fix the crisis.


Every horse’s fate was in my hands. No one knew how, or why, but their existence was threatened. They were many people’s favorite animal, and although cars and other vehicles had pretty much replaced them, they were still very useful.

Within this past decade, fertility rates have plummeted for stallions. Not only that, but nearly every foal ended up being a mare. At this rate, it wouldn’t be long until there were no males left. Which meant a solution needed to be found, and fast.

I had always been interested in science, namely biology. I also loved horses. As luck would have it, my career propelled me in the direction to work on finding a solution to this crisis. Being quite the renowned biologist, I had my very own lab at home. With the combination of my past achievements and my love for horses, I was awarded grants to help fund my research.

At home with me was my 18 year old daughter, Julie. She had transitioned years ago, and thanks to modern medicine, she now had the feminine body she always wanted. With lovely curves and a sizeable bust, it wouldn’t be hard for her to find a lover. Although she was very much a girl now, she felt confident with her dick and opted to keep it.

I spent months researching and trying to find out how to reverse the changes happening to horses. Even if I were to solve one of the problems, the other would still be threatening their continued existence. A stable had been installed on my property to store a few horses for me to experiment on. Whenever I thought I had made a breakthrough, the stallion that I had on hand just wouldn’t improve in terms of fertility. Everything felt futile.

Then, one day while staring at my notes, I realized that I might have been looking at all of this wrong. If stallions were doomed no matter what, then there was surely a way to impregnate mares some other way. Female horses weren’t affected at all in terms of fertility, though it wasn’t clear whether they were the reason that fewer and fewer stallions were being born. Genetic engineering has been an interest in the scientific community for years now, and has only recently become more commonplace and acceptable.

My theorized solution was altering a human’s body so that they could deliver viable seed directly inside of a mare. It would technically be considered bestiality, but if it meant the survival of horses, then so be it. With the last of my funding, I created a serum that hopefully worked. Now, I just needed to find someone to experiment on… I’d honestly use it on myself, but I was unfortunately not equipped to do the deed. Too bad my husband wasn’t around right now. It would have been hot watching him pump a mare full of fertile seed.

Nearing the end of the night, Julie came walking into the lab. She was still young and far from being as educated as I was, but she also loved horses very much. Her future plans even involved getting a degree in biology to maybe one day work alongside me in finding a solution.

“Make any progress today mother?” Julie asked.

I spun around on my wheeled stool. “As a matter of fact, I have.” I said, motioning towards my serum. “It’s a complete shot in the dark, but if it works… we just may guarantee there still being horses in the future.”

She smiled happily. “That’s wonderful news! I knew you could do it!” Running over to me, she hugged me tight. “But… what is it exactly?” She asked.

It felt awkward explaining it to her. “It’s a serum that should hopefully alter a man’s body so that his seed can be used to breed mares.”

Julie gave me a funny look. “You can’t be serious!” Then she noticed the very serious look on my face. “Things must have been dire if you went in that direction… Couldn’t improve the stallion’s fertility, could you?”

I shook my head. “Sadly, no. But now, I need to find someone to use this on. There’s a good chance that it won’t work, and there’s even the possibility that it has terrible side effects.”

Julie stood there thinking for a moment, then spoke. “Mom, I,” She hesitated before continuing. “I would be honored to have it tested on me.”

I completely forgot that Julie technically was viable, but how could I go through with that? “No way. I don’t want my own daughter to be an experiment. What if something went wrong!”

She stomped her foot on the ground. “Mom, I’m not a little kid anymore! I love horses as much as you, and you know we both would do anything to save them.”

Julie was right. She was 18 now, and I had no right to hold her back. “If that is what you wish, then I will support you. But we need to do this safely.”

“Thanks, mom.” She hugged me again. “I love you so much.”

“I love you too, dear.” I said.

My lab had some medical equipment in it, and a tall examination bed to lay on. I took the time to hook her up to the monitors so I could keep an eye on her. With the last sensor in place on her chest, I had her lay down on the bed while I retrieved the serum. I placed it into an injector gun, and returned to her side. The monitor was already beeping quickly as her heart beat in anticipation.

“Now, you’re absolutely sure you want to go through with this?” I asked her, hoping she’d change her mind.

Julie nodded her head. “Of course. You’re the only person I would ever entrust my wellbeing with. I know your serum will work.” She smiled.

Taking a deep breath, I held onto her arm and pressed the injector against her skin. I hesitated as long as I could. With a trembling finger, I pulled the trigger and watched as the liquid flowed into her body. The monitors immediately began beeping faster.

“How… how are you feeling?” I asked her.

“Other than feeling a pinch, I’m doing good.” Julie replied.

I pulled up and sat on the stool while keeping an eye on her. Nothing seemed to be happening, whether good or bad. Her vitals looked good, she still had a smile on her face, and my nerves calmed. I honestly wouldn’t be upset if nothing good happened, as long as she was fine once this silly experiment was over with.

Once ten minutes had passed, Julie alerted me to something. “I feel… I think I’m getting warmer.”

Standing up to feel her forehead, and looking at the monitor, she definitely had become a bit hotter. “You’ll be fine dear. Likely just a mild reaction.” I reassured her.

Her temperature slowly increased further, but never rose too much to be of any concern. Then I saw her fidgeting on the bed.

“Is everything okay?” I asked.

Julie blushed. “I’m fine, it’s just...” She bit her lip. “I think it’s making me a bit horny now.” She moved a hand over the front of her jeans.

I chuckled. “That’s nothing to be embarrassed about, sweetie. However, that might mean that it’s actually working!”

Over the next minute, her temperature, heart beat, and breathing increased some more. I tried to not stare, but I could see her adjusting the fabric of her pants as they began to bulge further. Watching her made me feel a bit hot as well, but I had to stay focused.

“Ohh...” Julie moaned softly. “Whatever that serum is doing, it’s making me feel very good...”

“Don’t hold anything back Julie. Let your mother know everything that it’s doing to you.” I said.

Everything increased yet again, getting to the point that her skin was becoming slick with sweat. While she was still far from having too high of a temperature, the constant increase was a bit concerning. But when her hand began to rub at her bulging jeans, I was just glad she was enjoying this.

“Mmm… I don’t… I don’t think I’ve ever been… this hard before...” She moaned deeply.

Now that I knew something was definitely happening to Julie, I stood up went right up next to her side. I couldn’t help but watch as she massaged that large bulge. We might have lived together and talked all the time, but I never realized just how big she was. It was making me miss my husband’s cock, who hasn’t been home for a few months now.

“Oh, Julie… your mother probably just whipped up an aphrodisiac or something!” I chuckled. “It could still bring us some money, despite not helping the horses.”

She moaned and massaged for a minute longer, then suddenly looked down at her pants worriedly. “Mom, it feels like… God, my pants are getting really tight!”

With her hand in the way the whole time, I only ever saw the general size of her bulge. But when she moved it away, I couldn’t believe what I was seeing. Her jeans were visibly swelling, stretching thinner by the moment. The monitor was beeping like crazy as her chest heaved. There was a subtle sound of threads snapping, and it was only a matter of time before she exploded out of her pants.

Julie’s hands began working frantically at her belt. “You have to help me. The pressure is becoming too much!”


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