No one can deny that the sight of a wiggling puppy evokes a smile on an otherwise dismal day, but the sight of thousands of unwanted puppies prompts dismay. The heat cycle, or estrus, is the period during which a female dog can be impregnated. Traditionally, spay surgery permanently prevents female dogs from going into heat. New contraceptives appear to do so impermanently.
The Heat Cycle
Once a female dog reaches puberty, she will begin experiencing the estrus cycle. In most dogs, the first estrus occurs at approximately 6 months of age and occurs every six months thereafter. Large breeds may not experience puberty until they are 18 to 24 months of age. Small-breed dogs may come into heat more frequently. Estrus is a natural cycle.
The Traditional Method
Also referred to as "in heat," or "in season," the estrus cycle is most often prevented by a spay surgery or ovariohysterectomy, During this surgical procedure, the ovaries and uterus are removed. The ovariohysterectomy is the most utilized preventative for unwanted pregnancies in dogs, and also is thought to protect the female dog from uterine, ovarian and mammary gland cancers.
Contraceptive Estrus Prevention
Contraceptives have been developed to prevent estrus and pregnancy as an alternative to surgical spaying. The Delvosteron or proligestone injection is a hormone injection that prevents estrus in female dogs. An initial injection is given, with followup injections administered three months later and again four months after that. Once the initial seven-month period has passed, injections are at regular five-month intervals. There is a slight increase in the occurrence of pyometras, a potentially life threatening infection of the uterus with the Delvosteron injection. In addition to injectable contraceptives, surgical implants, that control the reproductive system without the need for repeated injections, are under study.
The Best Practice
While contraceptives can serve to prevent estrus and pregnancy, the threat of cancer of the reproductive organs remains. To determine which method is proper for preventing estrus and pregnancy in your female dog, the best practice is to consult her veterinarian.