Let's say that you had your dog bred by a stud. Do you think his dick is cleaner than yours? Contrary to popular belief, a dog's penis is not really all that much more sanitary than a human's penis. They are both pretty unsanitary, but your bitch's vagina has a strong enough immune system that she probably won't croak from it.
Just don't do something stupid like drilling her like a jackhammer. I don't know what the deal is with men that do that.
The best fuck I got was from a very nice, handsome man that fucked me nice, slow, and deep. He wasn't rough. He insisted on using protection (I was naive enough to tell him he could but didn't have to, what a dumb child I was). He handled me as if I were the sweetest, kindest lady he had ever met, even though I am legally male. I look back, and I realize that, while I have no illusions that I ever could have counted on such a hot cad for fidelity, I am glad...oh, so glad...that I had the experience of getting fucked in the ass by someone that clearly had done it more than a few times before.
Start out nice and slow, and get into such a rhythm that she is moving like a dancer. Just watch how her body moves. If she is moving like she is dancing, then you are doing it right. Her body ought to be profoundly relaxed, and when her body is relaxed, her limbs move more freely and more fluidly, as if made out of springs.
Some guys, what they do is pound their bitches like a jackhammer, and I don't get it. I'm a gay bitch, and I don't care much for that, myself. It just upsets my stomach. Also, I would be concerned it could cause injuries.