I thought I would add this one to the other articles because of another thread where some questions were being asked. Good info here.
Do Aging Female Dogs Experience Menopause?
By Jocelynn Jacobs, DVM
Dr. Jacobs is a veterinarian, breeder, and exhibitor of Alaskan Malamutes. She has a breeder- referral practice where she works with breeders and owners of performance dogs.
I’m often asked as a breeder-veterinarian, “What will happen to my bitch when she gets older—will she go into menopause like people do?” “Should she be spayed?” “Will she eventually stop cycling?” “Do her chances of developing a pyometra increase as she ages?” These are interesting questions that deserve to be explored. Maintaining the health of our bitches after their reproductive years are over is important.
The Aging Ovaries
As your female dog enters her senior years and continues to have heat cycles, her ovaries may start to physically look abnormal. Normal ovaries are about the size and consistence of a soybean in small dogs and a lima bean in large dogs. Over the years, ovaries can develop pitting along their surface, or may develop cysts filled with fluid. During spays on older females, I have seen some ovaries look like a small piece of cauliflower with cysts and thickened tissue covering them. Ovaries continue to regulate hormonal releases, but as they age, they lose the efficiency to do it well.
The interval between heats may increase as your dog gets older, decreasing the number of times she goes into heat each year. In one report, 18-month-old dogs cycled an average of 1.65 times per year, while 7-year-old bitches cycled an average of 1.4 times per year.1 As your bitch continues to age past 7 years, fewer and fewer heat cycles occur. Eventually, your bitch may completely stop cycling. In this regard, it is similar to human menopause, but in dogs there are other considerations—mainly dealing with uterine health.
The Aging Uterus
The lining of the dog’s uterus is called the endometrium, and it remains proliferative (thickened) throughout its life. Many other species do not have proliferative uterine linings all their lives—this may be one reason dogs are unique when it comes to their aging reproductive tracts.
The ovaries and uterus use hormones to communicate to each other about reproductive status. The ovaries tell the uterine lining when to be ready for ovulation and when to go into estrus. The uterus tells the ovaries when it is pregnant.
As your bitch gets older, communication between the ovaries and uterus may not be as efficient as in her younger years. The proliferative lining of the uterus may undergo degenerative changes or excessive thickening because the communication between the two organs begins to fail. As the condition progresses, inflammatory cells appear in an effort to rid the uterus of excessive mucous or thickened tissue. Sometimes the uterus fills with high numbers of inflammatory cells and can develop a secondary bacterial infection. This is pyometra, a filled uterus, which can be a deadly condition if not treated by your veterinarian immediately.
So as your bitch ages, even though she may not cycle as often as she did in her younger years, the ovaries and uterus continue a not-so-effective form of communication, which eventually can cause pyometra. Therefore, to prevent this from happening, all female dogs should be spayed when they are no longer being used in a breeding program.
Is There a Magical Age?
Before a bitch of any age is bred, her overall health should be considered. In all instances, she should be in perfect health, but this is especially important when considering a bitch over 6 years old. All bitches over 6 years old should have a thorough examination by your veterinarian - no exceptions. Blood work and a urinalysis should be to screen for potential metabolic conditions or organ disease. The physically demanding needs of pregnancy or hard labor could heighten the conditions of a pre-existing disease and threaten the life of your bitch.
As bitches age, their fertility drops—their conception rates decrease and their litter size usually decreases. In one study, bitches between 3 and 5 years of age had the best conception rates and largest number of surviving puppies.1
So, if your bitch is in excellent health, how old is too old for her to be bred? In a survey conducted with breeders of small, medium and large breeds of dogs, they were asked at what age they usually stop using their bitches in a breeding program. The average was between 7 and 8 years of age.2 Keep in mind this was the average of many different breeds, and some breeders spay their bitches at an earlier age. Some breeders also consider the total number of litters the bitch has had when determining when to stop breeding—the more litters, the earlier they should be taken out of a breeding program. As a veterinarian, I recommend my clients have their bitches spayed by 7 or 8 years of age (or younger if the bitch is no longer being bred) to reduce the risk of pyometra.