I find it a little hard to comment on this, cause without the right words i feel my words easily get tacky.
Its such a taboo, and still somewhat it isnt. I have never read any statistics on this but from what I understand, many "normal/vanilla" (whats one to say...) people admit to being more or less aroused by watching animals breed. Like horse breeding.
For me the link from animal/animal to animal/human is not very far. Now offcourse, the reality of whats possible and whats just not, is considered in that comment, lol.
I know that from I was a little girl this has intersted me. Very taboo and very exiting. And this is quite common.
I remember crazy neighbourhood dogs humping on my leg, and one overthrew me when running with him in a leash. I remember watching animals on nature programs... Not much were more interesting and fascinating scary than to see big animals aroused. Its sex and its on display. Even if the species are different. It exites me.

The moral that has been debated here, I do agree on.
Its easier to wonder if the female animal gets abused than the male animal. But I find it hard to enter that debate. When I mentaly make an argument on one side, I just as easily can make a counter one, so I dont know what to say really.

But there is something so merciless about beastiality. And that I find very attractive.