Nasty.
Its called a Rim Job, a rim job is licking thee butt hole.
Yes.
Well it depends if she likes it
by licking my butt
Because it feels good and probally taste nice
It is simply a bad dog behavior.
licking butt
Your dog is not going to get sick from licking a cat's butt. Animals are always licking their butts.
No, but you can get a STD or infection.
Butt
This is normal, this is how they clean themselves. If, he is constantly linking there could be a problem, take your dog to the vet.
butt crack.