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: