I had a very close female work friend many years ago who was always pretty sharp and intuitive. We'd have flirty lunches together (we were both in other relationships), in which we'd both dance around our sexual histories, hang-ups, wants, etc. I never mentioned it directly to her - but once said something like "there are things I think about that i would never tell anyone" - and later that day she called me and asked very straightforwardly if it was anything to do with animals... Which broke the ice - yes, it's about animals, but it's not about me with them, it's about women I know with them... She asked if I'd thought about her with animals, to which my response was "I have now", which made her laugh... I should note, she was not into animals, but she was into fantasy (hers was that she got turned on thinking about women she worked with being raped - she felt guilty about it, but tried to remember that we can't control what we think about). When we became more 'intimate' (we were together for a little under a year) - we were able to enjoy a few shared fantasies about women she worked with being 'raped' by dogs... And even though rape is not my thing, and dogs weren't hers, it worked...
I've also 'confessed' my interest to my wife. Told her that the idea of a woman willingly, happily, giving herself to an animal is an incredible turn-on to me. She knows I've thought about her with dogs - again, like the ex, she has no interest in ever doing it herself, but she seems tolerant of my fantasies just as long as I don't go on and on about them. Any conversations on the subject are almost entirely one-way, but it's nice to be able to say something every now and then. I don't feel quite so alone.