I've had quite mixed results over 21 years of hoping for a beasty woman to share life with.
After my first girlfriends in my late teens, I started to be open and tell the women that I talked about sex with, after a few weeks, that I was into women getting bred by a dog or pony. 2 different women were interested, but they were the ones that I was not attracted to enough to date, and our lifestyles were too different.
I told my 3rd girlfriend at age 22. She didn't get it and would say no. Looking back, if we'd married, I bet she would have tried it after some kinky progression, and relationship sex becoming too routine.
At 23 I almost got back with my first love. She mentioned beasty stories. I admitted that I was interested in women getting mounted. I related it to our attempts earlier at fisting. She loved to feel stretched. Still, she quit talking to me over it and told her siblings. We were from a town of 2,500 people. Word gets around.
I was more reluctant after that. At 26 a woman that I hooked up with for buzzed casual sex said that she could see trying it, but after a drink and possibly with a blindfold. She was already into BDSM and infrequent group sex. So, it was about submission to her, but she didn't really want to try it. I talked about it other times, and she was changing her mind. The same exact thing happened with a different single mom that was from that same small town area. She said that she was interested on one or two phone calls, but months later she said no.
At age 30 a girlfriend almost broke up with me after finding out my fetish. She chose to overlook it though. During our last year together she was interested in trying Bad Dragon's horse cock dildo. I owned them for years, but it was too late by then. I felt that she was grasping for something to save us, and wouldn't really try a real horse anyway..... but I could be wrong.
Now at 40 I feel mixed about being forward with my fetish. In my mid 30's I told a few different trusted people in the kink community (one couple that leads events, and one buddy). None of them seemed to judge me, but they "didn't know of anyone into it" either.
A couple of different guys seem to have good luck being very forward about their fetish for this. That's great, but I'm gun shy. I met with a young woman from BeastForum a few years ago, and I think it was a setup. It was soon after I posted a pic of my gelding's cock. Silly me, they could tell if was a real pic and not one that I just found on the internet.
The woman that I'm currently dating knows, and she went through a couple of weeks of saying that she might try it, but she changed her mind. I wasn't even asking. She just knows it would really impress me. I could tell that's probably why she would try it, so I'm glad that she was honest with herself and decided that she probably would not do it.