Skip to main content

When is the “best” time to spay and neuter your pet?

To spay or not to spay (neuter as well), that is the question. Shakespeare posed that question many years ago, okay, maybe not THIS specific question, and it has been at the center of debate ever since. As always, a decision to spay or neuter your pet is best made between you and your veterinarian.

Both surgeries involve the removal of your pet’s reproductive organs. As we have come to understand, reproductive organs also function as endocrine glands. Endocrine glands produce hormones that affect other organs and processes within the body.

The timing of the surgery has recently been hotly debated, in the past several years there has been a great deal of information presented regarding long-term risks and benefits of spay and neuter surgery for your pet. The information is constantly evolving, and what we post today may be incomplete or even wrong in a few years.

Spaying or neutering your pet will eliminate any chance of unwanted litters. As you are probably aware there is a large problem with pet overpopulation. The veterinary community as well as rescue groups are trying to be proactive and advocate for responsible breeding practices. We are all too familiar with the hundreds of rescue organizations in our area and the herculean task of finding homes for all these unwanted pets. Unfortunately, these groups cannot help all stray pets and many thousands are euthanized, or die from trauma and disease every year. If you choose to not spay or neuter, remember, some dog parks, doggie day care centers, and boarding facilities will not allow an intact dog on the property. For female dogs, it is important that if you choose to wait until they are older, you will be tasked with managing an in-heat dog. At a minimum, this will involve keeping them separated from male dogs (not always as easy as you think), and managing vaginal discharge.

What do we know about the health risks and benefits?

While we know that these surgeries will reduce the risk of many cancers, such as testicular, ovarian, uterine, and mammary, we also have noted potential links to the increase of other cancer types with neutered pets. Some recent research shows a connection between early spay or neuter and a shorter lifespan, while other studies show a longer life for a spayed or neutered pet.

Cancer

Most studies have shown that the relative risk (compared to intact dogs), of mammary cancer increases after each heat cycle. For example, the risk of mammary cancer in a dog spayed before the first heat is 0.05% but becomes 100% after the 3rd heat. In cats, a 2006 study showed a 91% reduction in mammary cancer risk in cats spayed before 6 months and an 86% reduction when spayed before 1 year of age. Now there are questions about the methodology of some of the older studies, but it does appear that hormones play a role in the development of mammary cancer, the lower those hormones are, the less likely a pet is to develop mammary cancer. What about other types of cancer? Well, the studies there show mixed information, for example, the risk of osteosarcoma or bone cancer is about 3 times higher in both males and females, and the risk of mast cell tumors is 4 times greater in spayed females. There is currently not very much data on cat cancer risks.

Other health concerns

We know that neutered male dogs have a lower risk of perineal hernia, benign prostatic disease, perianal adenomas, and male-on-male aggression. Neutered male dogs, however, have a high rate of obesity, cruciate injuries (knee), diabetes, and hip dysplasia. Spayed female dogs have a decreased risk of pyometra (uterine infection) and ovarian tumors. Increased risks for female dogs include obesity, cruciate injuries, and a 5% risk of urinary incontinence. Now cats are a different story. We know that female spayed cats have a lower risk of pyometra but an increased risk of obesity and diabetes. Male neutered cats have a lower risk of roaming, fighting, and spraying in the house, but an increased risk of obesity and lower urinary tract disease.

All of these studies, however, have some flaws. While a connection may be present, there is not enough evidence to conclude there is a causation; one may not cause the other. The studies that have been done are exclusively large breed dogs, such as Rottweilers and Labradors. These results may not extend to dogs of different sizes, in fact, one study found different results in pointers as compared to retrievers, which are similar-sized dogs.

Broad recommendations are difficult to make and are best made for an individual pet with input from our medical team, however as a general rule:

Male cats

Neutering prevents behavioral issues making neutered male cats better pets. There are currently no major known health downsides to neutering cats.

Female cats

Cats should be spayed before or around 5 months of age to prevent mammary cancer which is highly fatal. Spaying also eliminates the risk of pyometra. And like the male cat, there are no major known health downsides to spaying.

Dogs with osteosarcoma or hemangiosarcoma predilection

This category applies to purebred dogs such as Golden Retrievers, Rottweilers, and Labrador Retrievers. These breeds, and others have a high propensity for very devastating cancers. Unfortunately, there are very limited methods to determine what any particular dog’s risk is for these diseases. Sometimes we can have some helpful information to guide us, for example, some breeders may share with you that these cancers are in their lines. However, some breeders may not be very forthcoming with this information. Recently, some blood tests have been introduced to look for the presence of nucleosomes, these can indicate an individual’s risk of cancer.

Large breed male dogs with a predilection to osteosarcoma and hemangiosarcoma:

In these patients, we should have a conversation about the risks and benefits. One option is to not neuter male dogs unless they have male-on-male aggression issues that cannot be addressed in other ways. If we are considering neutering, we recommend delaying it beyond 1 year of age to decrease the risk of osteosarcoma.

Large breed female dogs with a predilection to osteosarcoma and hemangiosarcoma:

We currently recommend neutering at 6 months of age to prevent mammary cancer, it will also eliminate the risk of pyometra. By neutering at this time, we may still have an increase in the risk of cancer, urinary incontinence, and orthopedic problems. We are not sure if waiting until after the first heat is protective. Of course, the other issue is if you are comfortable having a female in heat in your home.

Small and medium-sized female dogs without a predilection for cancer:

We recommend spaying at about 5-6 months of age to prevent mammary cancer and pyometra. We are unsure if there are risks of other cancers in the smaller dogs at this time.

As with any decision concerning your pet’s health, we invite you to become part of the discussion. Of course, our team only wants the best health for your pet. If you feel the need to search the internet, please limit your searches to reputable sites. Please ask us any questions that you may have, if we don’t know the answer, we have access to many reproductive and oncological specialists and can try to find the most relevant, recent information.