A few veterinarians have had moderate success (treating nymphomania in dogs) through massaging or rupturing the ovarian cysts by laparotomy. Sometimes effective treatment has been achieved through hormone injections that help to establish a normal and regular cycle. The success of therapy is not by any measure consistent. Most veterinarians recommend spaying as the normal and only viable course of treatment.
That's according to K9 Magazine's article on dog humping. Or, to put it more politely; excessive, unwanted mounting.Have a read! http://www.k9magazine.com/dog-humping/