weird but if they aren't harming anyone (or the animals) is it anyone elses business ?

Well, clearly, someone was harmed in this.

Another question is whether STDs/infections/diseases can be passed on (I honestly don't know).

We're talking about a different SPECIES. There's no concept of consent, no concept of conscious thought.

I'll go out on a limb here and make a blanket statement that anyone who does this is even more twisted/sick than a child molester.

To even entertain the idea that "if no one gets harmed, is it anyone's business" in this situation...it's a bit troubling to me.

Kevin