A redneck went to a bar and tied his dog to a tree outside.  While he was inside, a policeman came in and asked whose dog was tied up outside.
The redneck said it was his, and the policeman said, “Sir, I think your dog is in heat.”
The redneck said, “Naw, she ain’t in heat.  I tied her under a shade tree.”
The policeman said, “Sir, you don’t understand.  Your dog wants to be bred.”  And the redneck said, “Naw, she shouldn’t want any bread, I just fed her before we came here.”  And the policeman said, “Sir, you still don’t understand.  Your dog wants to have sex.” 
The redneck looks at the policeman and says, “Well, go ahead!  I always wanted a police dog!”