A female dog spayed before her first heat will have a near zero chance of developing mammary cancer. After the first heat, this incidence climbs to 7% and after the second heat the risk is 25% (one in four!). It is easy to see that an early spay can completely prevent what is frequently a very difficult and potentially fatal form of cancer.
But is it too late if a dog is already past her second heat? No, in fact spaying is important even in female dogs who already have obvious tumors. This is because many mammary tumors are stimulated by estrogens; removing the ovaries, the source of estrogens, will help retard tumor spread.
Spaying removes both the uterus and both ovaries and is crucial in the prevention as well as the treatment of mammary cancer.
The female dog comes into heat every 8 months or so. There is a bloody vaginal discharge and attraction of local male dogs. Often there is an offensive odor. All of this disappears with spaying.
What Is Pyometra?
"Pyometra" is the life-threatening infection of the uterus, which generally occurs in middle-aged to older female dogs in the six weeks following heat. The hormone "progesterone," which primes the uterus for potential pregnancy, does so by causing proliferation of the blood-filled uterine lining and suppression of uterine immune function. It is thus easy during heat, for bacteria in the vagina to ascend to the uterus to cause infection. The uterus with pyometra swells dramatically and is filled with pus, bacteria, dying tissue, and toxins. Without treatment, the pet is expected to die. Despite her serious medical state, she must be spayed quickly if her life is to be saved.
This is an extremely common disease of older, unspayed female dogs!
Pyometra is not something which "might" happen;
it probably will happen.
The older unspayed female dog has an irregular heat cycle. There is no end of cycling comparable to human menopause. If you still decide against spaying, be very familiar with the signs of pyometra. (These include loss of appetite, lethargy, vomiting, excessive thirst, marked vaginal discharge).
Spaying is one of the most important
preventative health measures that can be provided
for a female dog of any age.
What About Behavioral Changes?
The female dog's reproductive tract is dormant for most of the year. It only activates for the three week period of heat. This means that from a behavioral stand point, the female dog acts spayed most of the time. It is unlikely that any change will be evident.
The Health Benefits From Spaying
Are Too Important to Ignore.