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  • Writer's pictureJordin @ NLL

Appropriate age to spay/neuter your dog?


Historically, the appropriate age to spay/neuter your pet has been 6 months and this recommendation came from the desire to control the canine population and for the safety of the pet. Recently this age recommendation has changed for large breed dogs as more scientific research surfaces. Therefore, the question remains why do we castrate our pets, and at what age should we do so?

The gonadectomy refers to the removal of the gonads or reproductive organs and is the most routinely performed surgery among veterinarians. Removing the ovaries in females eliminates the secretion of estrogen and progesterone, whereas the removal of the testes in males eliminates the secretion of testosterone. Of course the most obvious benefit of removing the reproductive organs is the ability to regulate reproduction. Aside from controlling populations, the elimination of the sex hormones also results in a variety of behavioural and physical changes. Females will no longer go into heat which commonly causes swelling of the vulva and estrous bleeding and in males, mounting, roaming and sometimes aggression will be reduced. However, the removal of the sex hormones can have a much greater impact on the body than we once perceived. (Howe, 2015; Sorenmo et al., 2000; Johnston et al., 2001; Zink et al., 2014).


Cancer

The most common and well researched benefit to spaying your female dog is their reduced risk for developing mammary tumours (breast cancer). Many veterinarians believe that spaying must be done at six months to reap the benefits of avoiding this dangerous cancer. However, the risk of developing this cancer does not lie within the age of the dog but rather the number of heat cycles she has had. Females who are spayed before their first heat cycle have a 0.5% risk of developing mammary cancer, those who were spayed after their first heat cycle have an 8% risk, and those spayed after two heat cycles have a 26% risk. Since the average risk for any female dog that has had 2 or more heat cycles is 26%, many veterinarians argue that in order to reduce the risk of mammary tumours, dogs must be spayed before their second heat cycle. Therefore, if you do not plan to breed your dog, spaying for the purpose of reducing their risk of developing mammary cancer is recommended before their second heat cycle. (Howe, 2019; Sorenmo et al. 2000)


In contrast, males as a general population are at a much lower risk for developing cancers related to their sex hormones. Testicular tumours are one of the most common types of cancer diagnosed in intact male dogs (prevalence of 0.9%), however it is often benign (not harmful) and can be easily treated with the surgical removal of the testes (neutering). Another reproductive cancer diagnosed among male dogs is prostatic adenocarcinoma which is a highly malignant and fatal type of cancer. Surprisingly, the risk for developing this type of cancer increases about 2.4 to 4.3 times among neutered males. Further, prostatic adenocarcinoma is not the only cancer that becomes more common after a dog is neutered. Multiple studies have confirmed that transitional cell carcinoma, osteosarcoma, and hemangiosarcoma also have an increased incidence in neutered dogs compared to intact dogs. (Johnston et al. 2001; Zink et al, 2014)

Other Health Considerations


Non-cancerous reproductive disorders that do increase in prevalence among intact dogs are pyometra in females and prostatic hyperplasia in males.


Pyometra is an infection in the uterus and can be a fatal disease if left untreated. Females left intact are at a 25-66% increased risk for developing pyometra in their lifetime. Fortunately, if caught in time, antibiotic treatment and often a complete hysterectomy (spay) can resolve the issue. (Hagman et al. 2001)


In males, prostatic hyperplasia (cell overgrowth) is reported in 75-80% of intact males by the age of 6, and 95-100% by the age of 9. This disease can cause prostatic abscesses and cysts in males, and if left untreated can be fatal. Castration is not only a preventive measure, but the treatment for this disease. (Heuter, 2008)


Orthopedic Disorders

One of the most controversial and discussed health concerns surrounding age of alteration are orthopedic disorders. Hip dysplasia is common in many large breeds and although it is a multifactorial disease, research indicates an increased risk for larger breeds that are neutered at an early age. In a study of 759 golden retrievers, males that were neutered before the age of one had a 10.2% increased risk for developing hip dysplasia compared to intact males at 5.1% (Torres de la Riva et al. 2013). In a study of 1500 Labrador retrievers, they found that females who were spayed at <6 months of age had a 5.4% risk for developing hip dysplasia, 6 to 11 months had a 5.1% risk, 12 to 23 months had a 4.5% risk, and 2 to 8 years had a 0% risk compared to intact females with a 1.7% risk (Hart et al. 2014).


Another common orthopedic disorder that occurs often in larger breeds are cranial cruciate ligament (CCL) injuries (the equivalent of an ACL injury in humans). Multiple studies have confirmed that both males and females castrated before the age of one have a significantly higher risk of CCL rupture with the risk being even greater for dogs castrated <6 months of age (Whitehair et al. 1993).


It's important to remember that obesity and exercise regimes also play a role in the risk of CCL injury and orthopaedic diseases, as extra weight puts undo strain on the ligaments and promotes inflammation. Unfortunately, due to the decrease in metabolism following the removal of reproductive hormones, obesity is extremely common in spayed/neutered dogs, making their risk for CCL injury even greater. (Whitehair et al. 1993; Torres de la Riva et al. 2013)

Conclusions?


So how does one go about deciding the appropriate time to spay or neuter their dog, if at all? Multiple factors must be considered when making this decision, such as breed predispositions, health risks, behavioural compromises, and the owner’s willingness to act responsibly if they choose to spay/neuter at a later age. Overpopulation is a huge issue in North America, so if a dog is not going to be ethically and responsibly bred by a reputable breeder, it should spayed/neutered. For females, in order to avoid mammary tumours, spaying before their first heat cycle is most beneficial. If you own a large breed female, consider spaying after their first heat cycle to reduce the risk of hip dysplasia and CCL injury. For our female puppies, we recommend spaying after their first heat cycle, typically between 12-18 months of age. For males, the health risks are low when considering neutering. The behavioural benefits however are large, with decreased roaming, marking, and mounting. Consider your lifestyle, their predispositions, and their breed when choosing a time to neuter. For our male puppies, we recommend neutering between 18-36 months of age.


As always, talk with your veterinarian about what is best for you and your dog. Every pet is different and there is no 'perfect age' established for spaying or neutering your dog. Lastly, if you do decide to spay or neuter your pet at an older age, please, please be responsible.









References

Beauvais W, Cardwell JM, Brodbelt DC. The effect of neutering on the risk of mammary tumours in dogs--a systematic review. J Small Anim Pract. 2012; 53:314-322.

Hagman R, Lagerstedt AS, Hedhammar A, Egenvall A. A breed-matched case-control study of potential risk-factors for canine pyometra. Theriogenology. 2001; 17:1251-1257.

Hart BL, Hart LA, Thigpen AP, Willits NH. Long-term health effects of neutering dogs: comparison of Labrador retrievers with golden retrievers. PLoS One. 2014; 9:1-10.

Heuter KJ. Diseases of the prostate. In: Morgan RV, editor. Handbook of Small Animal Practice. 5th ed. St Louis: Saunders Elsevier; 2008: 559-568.

Howe L. Current perspectives on the optimal age to spay/castrate dogs and cats. Veterinary Medicine: Research and Reports. 2015;6

Johnston SD, Root Kustritz MV, Olson PN. Disorders of the canine testes and epididymes. In: Johnston SD, Root Kustritz MV, Olson PN, editors. Canine and Feline Theriogenology. Philadelphia: WB Saunders; 2001:312-332.

Sirinarumitr K. Benigh prostatic hypertrophy and prostatitis in dogs. In: Bonagura JD, Twedt DC, editors. Current Veterinary Therapy. 15th ed. St. Louis: Saunders Elsevier; 2014:1012-1015.

Sorenmo KU, Shofer FS, Goldschmidt MH. Effect of spaying and timing of spaying on survival of dogs with mammary carcinoma. J Vet Intern Med. 2000; 14:266-270. Top Health Concerns. (n.d.). Retrieved from http://www.akcchf.org/.

Torres de la Riva G, Hart BL, Farver TB, et al. Neutering dogs: effects on joint disorders and cancers in golden retrievers. PLoS One. 2013; 8:e55937.

Towle HA. Testes and scrotum. In: Tobias KM, Johnston SA, editors. Veterinary Surgery: Small Animal. St Louis: Elsevier Saunders; 2012:1907.

Whitehair JG, Vasseur PB, Willits NH. Epidemiology of cranial cruciate ligament rupture in dogs. J Am Vet Med Assoc. 1993; 203: 1016-1019.

Zink MC, Farhoody P, Elser SE, Ruffini LD, Gibbons TA, Rieger RH. Evaluation of the risk and age of onset of cancer and behavioral disorders in gonadectomized vizslas. J Am Vet Med Assoc. 2014; 244:309-319.

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