The issue is always one of informed consent...animals cannot verbally express their consent or lack thereof. We must also take into account if animals are of a level of intelligence whereby they can make an informed decision about their consent as well (answer: no).

If a woman gets on all fours and a dog mounts her, then it can be argued that the dog consents. Other scenarios are not so cut and dried.

Whilst this sort of thing isn't my bag, if I were a dog, I'd much rather be getting sucked off by some chick instead of being made into some Korean's dinner. I find it very odd when people object to people fucking animals, but not eating them.