I'm always going to be attracted to the large, powerful build of horses; mares specifically. Something about those wide hips and round butt. But I only become aroused by the bodies of horses, so long as the coat is cut extremely short and tight to the body; shaggy coats are a turn-off for me.
Even though I'm primarily attracted to mares, I still find myself staring at the genitalia of stallions. I love seeing huge stallion penises, but only in the context of watching beautiful women sucking and servicing them. I also look at the balls, and watch them bounce about as a woman tries her best to hide the horse's massive erection inside of her and jills herself by jerking his dick inside of her. Bonus points when there's horse semen leaking out of her before the stallion's penis is pulled out.
After horses, I'm extremely aroused by the massive udders of dairy cows and dairy goats; just the size and shape, and how its bulk spreads the legs of the cows and does. I will become extremely aroused at the sight (and idea) of seeing those udders either leaking milk, or seeing a mouth or a milking machine sucking on those teats. But again, the hair needs to be really tight against the bulk, otherwise I will get turned off.
I'm only aroused at the sight of large male dogs, but only because I begin to imagine them grappling a woman down and knotting them on the spot. Large dog bodies with massive genitalia, especially the balls as I get off in watching those balls flopping about while he pounds into a woman's poose. Extra bonus points when I see dog cum spilling out of her while the dog is still thrusting. Again, shagginess kills the mood; I lose the shape of the dog against the woman's body.
So basically, horses and dogs...so long as their coats are trimmed short and tight.