He hasn't been away from home for three years, but he is stalled next to geldings and he has a mare across the aisle. He has horses around him when he's in his paddock and they are all mares, as well as walking past mares and stallions in the barn as well as going to the arena. He is good with all of this.
A month ago Kristina was riding him in the outdoor and a friend had one of my mares to ride as well. Zing was a different horse and his behavior would not have been acceptable on a show ground. So, now we have been spending time reintroducing him to horses in the arena with him. I have only used geldings thus far, but the first time he was unruly throughout the ride. The next time he started out that way but settled down. After that he stopped paying attention. It's been about a week and a half since I had a gelding in with him, so today I used Spenser and Zing got up on his toes for about ten minutes and then settled down and went back to work.
I think one more time with a gelding and then I'll try it with a mare. We need him to be respectful so he can go for lessons and maybe start to show again. I know he will come back to himself as he was, but it sure was a surprise to me when he acted like a hormonal idiot!