I think the first was a childhood friend; I think I was 14 or 15 at that time.
We had been talking about stuff and eventually the topic of sex came up and I confided in him that I'd been having sex with the sows. He didn't believe me so we checked to make sure everyone else was distracted and we slipped off to where the sows were kept. They were quite familiar with the process by this time and the ones who were interested went into the building ahead of us, knowing what was coming. A bit of petting and a shamefully low amount of foreplay and I got behind my fav sow, pulled my dick out of my pants and started going to town. He started looking awkward and said something like, "I don't know if I would respect myself tomorrow" and just stood there; his loss, I finished what I was doing.
We never spoke about that again and I didn't tell anyone else for a few years. Many years later he joined some kooky church and got all judgemental, which, combined with time and other differences, drove a wedge between us that was large enough that neither wished to continue being friends.
I've often wondered if he ever came to regret that missed opportunity, probably not.