This is a difficult call considering that the male dog's behavior is carried out by instincts. Contrary to what you may have heard, many vets believe that nine is not old to spay a dog. Intact female dogs are particularly predisposed to pyometra and the chances of developing it increase as they age. Many vets think it is best to spay an older dog when they are healthy rather than spaying on an emergency basis when the dog is critically ill with life-threatening pyometra. An alternative option is to let the male dog wear belly bands for the duration of the dog's heat.