Im in grad school to become a therapist myself AND I recently saw a therapist to talk about my attraction to animals - so perhaps I have different layers of perspective with this question.
My therapist, in short, is amazing. I haven’t had many sessions since I can’t afford to go too often (grad school life lol). When I talked to him about having attraction to horses, he validated my perspective, saying that our culture really sexualizes animals in media, yet acts appalled when we actually experience attraction to animal shapes. Then, he asked me if having a sexual relationship with a horse is something that I’d want, or if I just wanted to spend therapy working on accepting my feelings. I was honest - saying that I’d eventually like to have a sexual relationship with a mare or stallion. He then talked to me about how he was aware that horses could be very receptive to human pheromones, and that a sexual relationship with one could very well be possible if I did it responsibly.
Lastly, I talked about how I would need to manage it while also being in a long term relationship with a human woman (my gf is well aware of my sexuality and supports me). He suggested that, because of my anxieties, I slowly warm up to the idea of actually fucking a horse. He proposed that first my gf and I fuck in a barn, then eventually have sex near a horse, then slowly start to incorporate the animal into my sex life after that. I could kiss the horse, give it a massage or bath, and then fuck my gf since I’d already be aroused from interacting with the animal. Eventually, if I’m safe and comfortable, I could start initiating more and more sexual contact with the horse.
I don’t know what specifically I’ll end up doing down the road, but it was amazing talking to someone who acted like what I was saying was totally normal. I’ll continue going to try to get more insight, and I’ll happily continue talking about my conversations in therapy.