well to start i'll say, even if they are trained in this way, is it abuse if it feeds their nature?

id say a man with a female animal would be considered abuse as someone stated earlier, just because even if you wanted to claim "well she was in heat!" or some such, its not quite the same as a dog willingly humping someone.

And as for your question blythe, im not a woman so im not sure it would quite apply to me -wryly- somehow I dont think a dog would take to oral sex on a man to anywhere near the same degree as a woman

That being said, and If im wrong I dont mean to put words in any womans mouth, however I mean, a tongue is a tongue, a dog tongue might have a different texture, but id imagine the pleasure would be the same, perhaps not as skilled though as a human who knows what he/she is doing.

But in the end it seems that a scene like you described, if you never knew it was a hound going at you, or which sex it was, then its perhaps a literal approach to ignorance is bliss.