While elective gonadectomy is one of the most common veterinary surgeries performed in North America, little data exist to
suggest the optimal age (Kustritz 2007). Prepuberal gonadectomy refers to gonadectomy before the onset of puberty, which may
occur in female cats between 4 and 21 months of age and in male cats between 8 and 10 months of age. Early age altering (EAA)
refers to gonadectomy between 6 and 16 weeks of age and is more commonly practiced as veterinarians gain experience with pediatric
anesthesia and surgery. EAA is one useful approach for control of pet overpopulation as it enables shelters and pedigreed
breeders to perform pre-adoption altering and avoids the risk of owner non-compliance with altering contracts. Increasingly,
it is recognized there are also health benefits to EAA.
Objections to EAA have included concerns about effects on growth, increased femoral fracture risk, obesity, behavioral changes,
increased disease risk, and safety of anesthesia and surgery in pediatric patients.
Testosterone and estrogen assist maturation of the physes in long bones. Growth stops when physeal closure occurs. Intact
cats have distal radial physeal closure at 1 year of age or older. Cats altered at 7 weeks and 7 months of age had distal
radial physeal closure about 8 weeks later than intact cats (Stubbs, Bloomberg et al. 1996; Root, Johnston et al. 1997). The
effect of this delay in physeal closure is unknown, but adult size in cats is not significantly affected by age of altering.
It has been suggested that delayed physeal closure may predispose cats to Salter fractures of the femoral capital physes.
The femoral capital physis normally closes between 7.5 and 10 months of age. Other risk factors for this type of fracture
include obesity and gender/reproductive status (neutered male) (McNicholas, Wilkens et al. 2002). The risk of fracture would
be the same for cats altered at any age that results in delayed physeal closure, not just EAA cats. These fractures appear
to be rare in the altered cat population. One large study failed to find any association between EAA and physeal fracture
risk in cats (Spain, Scarlett et al. 2004).
Obesity is a multifactorial problem involving diet, exercise, age and other factors. Altered cats have a lower metabolic rate
than sexually intact cats regardless of the age at gonadectomy. Altered male cats require 28% less calories than intact male
cats and altered female cats require 33% fewer calories than intact female cats (Root, Johnston et al. 1996). Clients should be counseled on the dietary and exercise needs of altered cats to avoid obesity.
Compared to altered cats, sexually intact cats show less affection to humans and more aggression to other cats. One study
has shown that EAA male cats are less aggressive to vets, and exhibit fewer problems with urine spraying (Stubbs, Bloomberg
et al. 1996). Other long term studies have shown there is no difference in the prevalence of significant behavior problems
based on age at altering (Spain, Scarlett et al. 2004; Wright and Amoss 2004).
Lower urinary tract disease in cats is a diverse collection of conditions caused by a wide variety of factors such as diet,
water intake and stressors. The diameter of the male urethra is no smaller in EAA cats than in intact cats (Root, Johnston
et al. 1996). Age at altering does not influence risk of urinary tract disease; in fact, one study showed a lower risk of
urinary tract obstruction in EAA male cats (Spain, Scarlett et al. 2004).
Several long term studies have been performed to assess health risks of EAA. These studies confirm that EAA is not associated
with any increased risk of disease, but rather is associated with a lower risk of some diseases, such as asthma, gingivitis,
mammary carcinoma (Howe, Slater et al. 2000; Spain, Scarlett et al. 2004; Overley, Shofer et al. 2005).
Anesthesia and Surgery
Pediatric patients have unique perioperative, anesthetic and surgical issues (Kustritz 2002). Kittens should have a complete
physical exam as well as the first vaccination and treatment for parasites before surgery; postpone surgery if any illness
or abnormality is found (including cryptorchidism). Anesthesia and surgery do not affect response to vaccination so that kittens
can be vaccinated at the same time as surgery if required (Levy, Reese et al. 2006).