I got bored and created a throwaway account on reddit. I made a post. I fully expect the reddit gods... err... umm... MODS to delete my comment and also ban my throwaway account, but here's what I posted...
"It's really not hard to discern whether or not a dog wants to engage in sexual behaviors. The most important thing is that you have let the dog choose on it's own whether or not it wishes to engage in said behaviors with a human. As someone mentioned before there is a master/subservient power dynamic aspect you have to contend with. The easiest way one could overcome this is to simply read the dog's body language, as that's their most effective way of communicating.
Is the dog showing signs that it is making sexual advances towards you? For example, if a female dog is flagging you? (parting her tail to the side to expose her private bits) Is she backing herself towards you? Does she seem excited? Are you engaging with her as a male dog would with a female dog during a mating courtship? If the answer is yes, then any sexual encounter would more than likely be viewed as enjoyable for the dog. When mating, dogs are shown to release the brain chemicals: dopamine, oxytocin, and vasopressin, which are the same chemical released by humans while engaging in sexual activities.
Is she rejecting sexual advances? Backing away from you? Has her tail tucked between her legs. Looks apathetic and maybe even fearful. Possibly even growling/whining at you? If the dog is displaying signs that it is uncomfortable then any further sexual advances would be considered forceful and even rape. If a human wishes to be involved this way with an animal, it's important that the animal reciprocate these feelings. It's also important not to acclimate the dog towards sex. They call all the shots, not you.
I'm not arguing whether or not bestiality should be normalized within society or not. A matter of fact, I don't think it will ever be. This is due to the animal's inability to speak out against any sexual abuse it may receive from a human that doesn't wish to let the animal choose whether or not the activity is even wanted in the first place. My argument is that if you let the dog decide whether or not it WANTS to engage in this activity, then bestiality can be essentially harmless. Dogs live in the moment after all. If it feels good, then they'll seek it out on their own terms. No coercion is needed. You also have to remember that sex is not sacred for an animal, it's driven by lust and an instinct to pass along it's genes alone."
Let the FUN begin!