Navigating the Spay & Neuter Timeline Debate
Navigating the Spay & Neuter Timeline Debate
(NCCF Blog Post – May, 2021)
For many years, I have recommended to clients that they should spay or neuter their canine companions by 6-7 months of age (prior to sexual maturity) if breeding isn’t in their future. This recommendation has largely been based upon information that I learned in veterinary school and the serious pet overpopulation problem that plagues the United States today.
If you live in the United States and grew up with pets, spaying/neutering your dog probably feels like a normal and logical thing to do. Even on The Price Is Right as far back as 1982, Bob Barker always ended each show with the phrase: “This is Bob Barker reminding you to help control the pet population – have your pets spayed or neutered.” Many of us grew up believing that spaying/neutering our dogs was part of the “normal” course of their lives.
Within the last decade, however, there has been ongoing research with regards to the appropriate age at which to spay/neuter dogs and whether or not it should be recommended at all if there is no health concern present. Major concerns about the increased risk for certain forms of cancer and orthopedic diseases in dogs have been brought to light because of the data collected from this research.
If you look at all of the research projects and studies that are out there concerning this subject, you will find some consistent and some conflicting data. As a pet parent, this information may be confusing and may lead to agonizing over the “right decision” on when to spay/neuter your dog, or whether to do it at all! What we thought we knew about the subject may not nearly be all that there is to know. We, as pet parents, are good-intentioned and want what’s best for our canine counterparts. When we hear the rumblings of the word cancer mixed in with the subject of spaying/neutering dogs, it tends to cause us to stop abruptly and take notice!
How, then, do we go about navigating the growing controversy surrounding when (and if) to spay/neuter our canine companions? You could survey 3 different veterinary clinics in your area and likely come up with 3 different recommendations on the subject, nowadays. Do you turn to your general veterinary practitioner for this information, a board-certified veterinary surgeon, a board-certified veterinary oncologist, or a shelter medicine veterinarian? Each of those types of veterinarians could have slightly different recommendations based on their personal experiences.
Because there is now so much information out there on this topic, we could potentially become very nervous about making the “right decision.”
For me, personally, helping clients make this important decision for their dogs comes down to one very important idea – one size does not fit all.
What do I mean by that?
Each dog should be evaluated separately when attempting to make this type of decision. We need to look at several factors before making a decision on when (or if) to spay/neuter a dog:
● What breed of dog is it?
● Is the dog male or female?
● What is the current age of the dog?
● Are there other intact dogs in the household?
● Does the dog spend time unattended outside?
● Does the dog roam free outside of the yard?
● What is the current health status of the dog?
● Is there a signed contract from a breeder/adoption agency with any specific requirements for spaying/neutering?
● Are there plans for breeding this dog?
Once these important questions have been answered, we can then look at the current information that is out there with regards to timing of spaying/neutering dogs.
So, what factual information is out there that may help us to determine when to spay/neuter our dogs? For the purpose of this blog post, I will be concentrating more heavily on information related to canine cancer. However, we should take a look at a few other bits of factual information first:
Pet Overpopulation
✔ Spaying/neutering dogs helps to control pet overpopulation in the United States. A few decades ago, a shocking 13-15 million dogs and cats were euthanized each year in animal shelters due to lack of space. With the establishment of spay/neuter protocols, those numbers have now decreased to 1.5-2 million each year (still a staggering number).
✔ Many animal shelters require all adopted pets to be spayed/neutered prior to going to their new homes or to be spayed/neutered within a certain time frame after entering their new homes.
Reduced Risk for Canine Pyometra and Mammary Cancer in Spayed Females
✔ Intact female dogs have an overall 25% likelihood of developing pyometra (infected uterus) at some point in their lives. Pyometra can be life-threatening if not caught and treated early.
✔ The incidence of mammary tumors in female dogs is approximately 3.4%, and there is a strong correlation between the age at which female dogs are spayed and the development of mammary tumors.
o Dogs spayed prior to their first heat cycle have a 0.5% risk of developing a mammary tumor.
o Dogs spayed after their first heat cycle (but prior to their second) have an 8% risk of developing a mammary tumor.
o Dogs spayed after their second heat cycle have a 26% risk of developing a mammary tumor.
▪ If they are less than 2 ½ years old at the time of spay, this risk drops to 6%.
▪ If they are over 2 ½ years old at the time of spay, this risk jumps to 40%!
✔ The incidence of mammary tumors in female dogs increases with age and with exposure to sex hormones. The highest risk for mammary tumor development appears to be between 7 and 13 years of age.
Reduced Risk for Reproductive Organ Cancer in Spayed/Neutered Dogs
✔ When female dogs are spayed, we are eliminating the risk for ovarian and uterine cancer.
✔ When male dogs are neutered, we are eliminating the risk for testicular cancer.
✔ Interestingly, neutered male dogs have a 2-8x increase in the incidence of prostatic carcinoma (the most common form of prostate cancer).
o Prostatic carcinoma, overall, has a prevalence of <1% in the canine population.
Increased Risk for Orthopedic Disease in Spayed/Neutered Dogs
✔ Some studies suggest that hip dysplasia, cranial cruciate ligament rupture, and elbow dysplasia may have a higher rate of occurrence in certain breeds of dogs spayed/neutered prior to 1 year of age.
o Golden Retriever Study (2013)
▪ Males neutered prior to 1 year of age had a 10% incidence of developing hip dysplasia.
▪ Males neutered prior to 1 year of age had a 5% incidence of developing cranial cruciate ligament rupture.
▪ Females spayed prior to 1 year of age had an 8% incidence of developing cranial cruciate ligament rupture.
o Golden Retriever and Labrador Retriever Study (2014)
▪ Golden Retriever results were similar to the 2013 study.
▪ Male Labradors neutered prior to 6 months of age had an 8% incidence of developing cranial cruciate ligament rupture.
▪ Male Labradors neutered prior to 6 months of age had a 4% incidence of developing elbow dysplasia.
▪ Female Labradors neutered prior to 1 year of age had a 5% incidence of developing hip dysplasia.
Keeping all of this information in mind, we should now take into consideration that certain breeds of dogs appear to be at increased risk for different types of cancer, depending on when they are spayed/neutered:
1) Lymphoma (LSA)
❖ Golden Retrievers
➢ Males neutered between 6 and 11 months of age had an 11.5% incidence of developing LSA (versus 4% for intact males).
➢ Neutering prior to 1 year of age appears to increase the risk 3X in males.
➢ Age of spaying did not appear to have a significant effect on the incidence of females developing LSA.
❖ Labrador Retrievers
➢ Age of spaying/neutering did not appear to have a significant effect on the incidence of male or females developing LSA.
❖ Vizslas
➢ In one study, there was a 4.3X increase in the likelihood of developing LSA in all spayed/neutered dogs, regardless of the age at which they were spayed/neutered, as compared to intact dogs.
2) Osteosarcoma (OSA)
❖ Rottweilers
➢ In one study, there was a 3-4X increase in the development of OSA in dogs that had been spayed/neutered prior to 1 year of age.
3) Mast Cell Tumor (MCT)
❖ Golden Retrievers
➢ In one study, MCT was diagnosed in 2.3% of females spayed prior to 12 months of age and 5.7% of females spayed at 12 months of age or older.
➢ In one study, there appeared to be no correlation between MCT incidence and age of neutering in males.
❖ Labrador Retrievers
➢ In one study, there did not appear to be a correlative effect between MCT formation and age at spay/neuter.
❖ Vizslas
➢ In one study, there was a 3.5X increase in the likelihood of developing MCT in all spayed/neutered dogs, regardless of the age at which they were spayed/neutered, as compared to intact dogs.
4) Hemangiosarcoma (HSA)
❖ Golden Retrievers
➢ In one study, females spayed at 12 months of age or older were 4X more likely to develop cardiac HSA and were 2X more likely to develop splenic HSA than intact females or females spayed prior to 12 months of age.
➢ Age of neutering did not appear to have a significant effect on the incidence of males developing splenic HSA.
❖ Vizslas
➢ In one study, there was a 9X increase in the likelihood of developing splenic HSA in spayed female dogs as compared to intact dogs.
Are you bogged down with this information yet? I certainly was when I first sat down to research this spay/neuter timeline debate! What’s extremely important to take away from all of this data is the following:
● There does appear to be a correlation between the age of spaying/neutering and the risk of developing certain forms of cancer in certain dog breeds. Specifically, lymphoma, osteosarcoma, mast cell tumor, and hemangiosarcoma have been shown to develop more frequently in certain breeds of dogs spayed/neutered at a young age.
● There does appear to be a correlation between the age of spaying/neutering and the risk of developing certain orthopedic conditions in certain dog breeds. Specifically, hip dysplasia, cranial cruciate ligament rupture, and elbow dysplasia have been shown to develop more frequently in certain breeds of dogs spayed/neutered at a young age.
● Spaying female dogs prior to their first heat cycle nearly eliminates the risk for the development of mammary cancer. However, be aware that 50% of mammary tumors are benign, and 50% are malignant. 50% of the malignant tumors can be cured with surgery alone! If you are diligent about checking your female dog over once a month for lumps and bumps, you are likely to catch these mammary tumors when they are small and be able to have them evaluated quickly! This information may help you to decide on whether or not to spay your female dog at an early age versus waiting, especially if she is one of the breeds at risk for orthopedic disease or cancer development.
It is important to remember that these aforementioned studies, for the most part, looked at specific dog breeds and the development of orthopedic disease and cancer. While it would be nice to extrapolate this data onto all breeds of dogs, we unfortunately cannot do that at this time. We cannot make a blanket statement about the appropriate age of spaying/neutering our canine companions - too many factors appear to be involved!
At this time, it makes the most sense to treat each dog as an individual when trying to decide when the “right time” is to spay/neuter them. If your best friend is one of the breeds listed above, it may seem more appropriate to wait to have them spayed/neutered. It is unclear at this point in time just how long to wait. Hopefully, additional data will be revealed in the near future to assist us in making this decision more easily.
You were probably hoping for a magic formula at the end of this blog post to help you decide when to spay/neuter your best buddy. I truly wish that it were that easy! A decade ago, it was that easy . . . because we didn’t know any better! With advancements in veterinary medicine occurring every single day, we must stay relevant and provide our dogs and cats with the absolute best care that we possibly can. Talk with your veterinarian about spaying/neutering your dog. Answer the above questions outlined at the beginning of this blog post to help shed some light on your dog’s specific needs. For instance, if you have a 1-year-old female Golden Retriever who spends a great deal of time outside and may come into contact with an intact male dog, you may want to have her spayed regardless of the data, just to avoid an unwanted pregnancy! You have to look at the whole picture prior to making this kind of decision.
In any case, this information should make us all pause, take a step back, and look at the whole picture. That way, we can make an educated decision about when it is the “right time” for us to have our dogs spayed/neutered. Perhaps, your decision won’t be the same as your neighbor’s. That doesn’t make one person right and the other person wrong. We have to look at all of the factors involved and make a decision that appears to be best for everyone involved.
References
Dr Sue Cancer Vet - VLOG 62 - “When is the Best Time to Spay or Neuter Your Dog?”
Kirkby, Kristen - “Cancer vs. Cruciate: The Debate Over Early Neutering” - NAVC Small Animal Conference - March 8, 2019
Goh, Clara - “Age of Neutering in Large and Giant Breed Dogs: A Matter of Opinion” - Clinician’s Brief - August, 2016
Berg, John - “The Spay/Neuter Controversy and Topics in Genital Surgery” - Video Surgery
Intile, Joanne - “The Role of Neutering in Cancer Development” - Lecture Notes
Smith, Annette - “The Role of Neutering in Cancer Development” - Veterinary Clinics Small Animal 44(2014) - Pages 965-975
Torres de La Riva, Greta, et. al - “Neutering Dogs: Effects on Joint Disorders and Cancers in Golden Retrievers” - PLOS ONE Volume 8(2) - February, 2013
Petty, Michael - “Re-examining the Early Spay-Neuter Paradigm in Dogs” - DVM360 Volume 50(4) - April, 2019
Hekman, Jessica - “Do Spayed and Neutered Dogs Get Cancer More Often?” - Scientific American - February, 2015
www.aspcapro.org - “Dealing with Concerns About Pediatric Spay/Neuter”
Hart, Benjamin, et. al - “Long-Term Health Effects of Neutering Dogs: Comparison of Labrador Retrievers with Golden Retrievers” - PLOS ONE Volume 9(7) - July, 2014
Bentley, Adrienne, et. al - “Controversies in Spaying and Neutering: Effects on Cancer and Other Conditions” - Cornell University Veterinary Specialists - Stamford, CT