Thank you very much, All!
I'll talk to the owner explaining her situation (BTW, I'm not 100% postitive, but I believe it's a barbered wire there used as fence). My neighbor, who is also very concerned because of her OTTB, plans on suggesting her to geld the stud. HOWEVER I HIGHLY doubt she'll listen. Some time before I moved to this place that person had full size stud (arab, I believe?), who drove my neighbor's mare crazy running and screaming like that, and obviously that lady didn't care a bit about it (not sure what happened to him, either he got injured or she just sent him to the auction after ### of years owning him).
So if worst comes to worst, WHO should I contact about the stud? Animal Control?