Yes my wife knows and I've had sex with mares in front of her. She does not join in, it's not her thing, but she doesn't mind if I have a "quicky" once in a while. Were both into horses and both have mares, Few months into our dating, I would joke that "I'm going to do it with my mare" (I've already been fucking mares for years.) She would be like "why?" and "no you wouldn't!? I just said I wanted to see what's it like and if my mare would let me.
She never got angry or grossed out when I brought it up. So watching tv one day, I started to laugh and she asked whats so funny? I came clean and told her I did it with her. She didn't believe me an after a bit. I showed her a couple pictures of my dick in my mares pussy as proof. She just went why and I didn't know people do stuff like that. I just said, honestly IDK I liked it. She ended up being fine with it and later I confessed I've been at it much longer. She doesn't like if my clothes stink like in heat mare. Once she got upset, I was helping her with cleaning the stalls. She popped in the arena and was like "I knew it, your supposed to be helping with stalls, not fucking my horse." Hay her mare was willing, so a I grabbed a quick one while emptying the cart. She was ticked off even a bit after cause I heard her say "now her tail's up" when she walks around after. Other wise she's joked to dump water on us. Been married for nearly 10 Years. Just addicted to mares, LOL!