I haven't noticed many inputs in this thread from male submissives. To qualify what I am about to say, this desire, about which I have mixed feelings, is not something that I have ever done.

I was in a casual relationship with a dominant female Air Force nurse. She had two large dogs. One afternoon she told me that she wanted to watch me suck off her male dog and that she intended to make sure that I did just that -- using as much force as necessary to get me to comply (obviously, for this "little" scenario I would first be somewhat bound, albeit in a vulnerable position). Ironically/fortunately, she got orders to ship out to Bahrain before her desire reached a point that she acted upon it.

Nonetheless, to this day, the idea of submitting to so much perverse power, as distasteful as the actual act would be, has had an erotic hold on me.