Just try your best to keep in mind that, PARTICULARLY IN THE USA, "LEGAL" only means there is no explicit "you're a criminal if you stick your johnson in an animal/allow an animal to stick his johnson in you" law on the books to charge you with. Expect that if you get busted, you're still pretty well fucked (and not in a good way) 'cause they're gonna throw everything that even kinda-sorta-almost seems applicable - starting with some variation of "animal cruelty", "animal abuse", "animal mistreatment", or similar - at you, and you can pretty well guarantee that at least one of the charges they dream up WILL "stick", putting you on the sex-offender list, probably barring you from having any unsupervised-by-an-approved-person contact of any kind with any animal, and more than likely resulting in the critter involved being killed.