What is the Best Age to Perform Spays & Neuters?

There is an increasing, though controversial, body of evidence calling into question the pros and cons that early spay/neuter may have on cats and dogs.  The AVMA, “supports the concept of pediatric spay/neuter in dogs and cats in an effort to reduce the number of unwanted animals of these species.”   Our professional association also advises that, “veterinarians should use their best professional judgment based on the current scientific literature in deciding at what age spay/neuter should be performed on individual animals.”

So what is that scientific literature?

A concise summary would indicate that in males the pros of early neutering include: elimination of testicular cancer, near elimination of non-neoplastic prostate disease and decreased risk of perianal fistulas.  The pros of early spay in females include: decreased risk of mammary neoplasia (recently challenged), elimination of pyometra, decreased risk of uterine and cervical disease and easier control of seizure and diabetes management.  Both males and females have increased longevity.

The literature would assess the following potential risks associated with early spay/neuter:   Delayed growth plate closure, physeal dysplasia in male cats leading to capital physeal fracture, higher prevalence of CrCL disease and hip dysplasia in dogs, increased risk of osteosarcoma, hemangiosarcoma, lymphoma, mast cell disease, recessed vulva, urinary tract tumor, hypothyroidism, obesity, urinary incontinence and infection, adverse vaccine reaction and geriatric cognitive impairment.

Generally, the study design for the majority of the body of literature on this topic is subject to Type I error (“false positives”) and is conducted on relatively small populations.  Also, pet owners that elect early spay/neuter are much more likely to seek veterinary care for any of the clinical signs associated with the diseases above when compared with the pet population that does not undergo de-sexing which further contributes to type I error.  One might also expect that increased longevity would simultaneously increase risk of neoplastic disease.

All of this literature must be taken together with clinical experience in order to make tailored recommendations to clients for their individual pet.  Generally, (and outside of a shelter/rescue environment), it seems sensible to continue to recommend ovariohysterectomy or ovariectomy prior to first estrous while offering increased consideration to delaying castration until skeletal maturity is reached – for most breeds around 13 months.

Abbreviated list of References:

1. Beauvais W, Cardwell JM, Brodbelt DC. The effect of neutering on the risk of mammary tumours in dogs - a systematic review. Journal of Small Animal Practice. 2012a;53:314–322.
2. Beauvais W, Cardwell JM, Brodbelt DC. The effect of neutering on the risk of urinary incontinence in bitches - a systematic review. Journal of Small Animal Practice. 2012b;53:198–204.
3. Duerr FM, et al. Risk factors for excessive tibial plateau angle in large-breed dogs with cranial cruciate ligament disease. Journal of the American Veterinary Medical Association. 2007;231:1688–1691.
4. Howe LM. Short-term results and complications of pre-pubertal gonadectomy in cats and dogs. Journal of the American Veterinary Medical Association. 1997;211:57–62.
5. Spann AC, Wilkiw WS. Long-term outcome of gonadectomy performed at an early age or traditional age in cats. Journal of the American Veterinary Medical Association. 2000;271:1661–1665.
6. Salmeri KR, Olson PN, Bloomberg MS. Elective gonadectomy in dogs: a review. Journal of the American Veterinary Medical Association. 1991;198:1183–1192.
7. Spain C, Scarlett JM, Houpt KA. Long term risks and benefits of early age gonadectomy in cats. Journal of the American Veterinary Medical Association. 2004;224:372–379.
8. Spain C, Scarlett JM, Houpt KA. Long term risks and benefits of early age gonadectomy in dogs. Journal of the American Veterinary Medical Association. 2004;224:380–387.
9. Craig, LE. Physeal Dysplasia with Slipped Capital Femoral Epiphysis in 13 cats. Veterinary Pathology January 2001 vol. 38 no. 1 92-97
10. Slauterbeck JR et al. Canine ovariohysterectomy and orchiectomy increases the prevalence of ACL injury. Clin Orthop Relat Res. 2004;(429):301-5.
11. Whitehair JG, e. Epidemiology of cranial cruciate ligament rupture in dogs. JAVMA 1993;203:1016-1019.
12. Schneider et al. Factors influencing canine mammary cancer development and postsurgical survival. J Natl Cancer Inst 1969
13. Overly B et al, Association between ovariohysterectomy and feline mammary carcinoma. JVIM 2005, 19, 560–563.