One summer when I was about 13 my mom, very out of character, made me go work at a horse ranch for a few weeks. I have never been around or even really thought about horses at all. I was asked to sweep the entire floor of the very long concrete stable floor, something I enjoyed doing. Then I saw them, the freakishly massive animals I'd only ever seen in cowboy shows. They equally scared the shit out of me and fascinated me. They were so large but so calm and friendly, in their eyes I could see real intelligence.
Now I don't know if this ranch was some secret zoo ranch or something but all the horses there were horny as hell those weeks. And being a child of the American Education system I was never taught about sex or anything of the like so seeing mares flash me and stallions with dicks the size of my arm I was shocked and they had to have known it. From that day forward horses have seemed hot as hell for me.
So I blame those horses for starting it and flirting with a young child XD