Desexing of dogs and cats

Desexing of dogs and cats

Policy type: Policy
: 9b
: Current
Date ratified
: November 2018

NZVA Policy

The New Zealand Veterinary Association (NZVA) supports surgically de-sexing all cats and dogs that can safely undergo anaesthesia and are not intended for breeding. Surgical de-sexing manages both the significant welfare problems associated with unwanted cats and dogs as well as providing health benefits to individual animals.

Age of de-sexing

Accounting for both the known benefits and potential risks associated with de-sexing, the NZVA recommends:

  1. Pre-pubertal de-sexing of all cats that aren’t intended for breeding and are fit to undergo anaesthesia(1).
  2. Due to the complex nature of potential risks and known benefits associated with pre-pubertal de-sexing in dogs, no single recommendation is appropriate for all dogs. For the majority of dogs that aren’t intended for breeding and are fit to undergo anaesthesia, pre-pubertal de-sexing of dogs is supported.
  3. There are however, specific populations of owned dogs, in which breed, genetic predisposition and lifestyle factors suggest delaying de-sexing until after puberty may provide a health benefit. Veterinarians should therefore weigh both the risks and benefits of pre-pubertal de-sexing for individual dogs, in consultation with their owners to determine the most appropriate age to undertake de-sexing.


De-sexing procedure

While considered a routine operation, de-sexing cats and dogs is a significant surgical procedure that must only be undertaken by a veterinarian, or a veterinary student under the supervision of a veterinarian.

As with all surgical procedures, the veterinarian must be satisfied that the patient is fit to undergo the procedure, is properly prepared and ensure any anaesthetic risks are identified and managed.

As de-sexing is a painful procedure, analgesia must be included in the planning. Veterinarians are referred to the WSAVA pain management guidelines(2,3) for examples of drugs and duration of treatments post-operatively.

While ovariohysterectomy is the most common procedure for de-sexing female cats and dogs in New Zealand, ovariectomy is a valid alternative common in Europe with no significant differences in outcomes(4). There is also no reported increase in the risk of pyometra with ovariectomy(5).

Positive benefits of de-sexing

Research reveals that de-sexed animals live longer lives(6).

De-sexing will benefit individual cats and dogs by:

  • Eliminating the risk of uterine infections in females. Around a quarter of female dogs can be expected to experience pyometra by ten years of age if not de-sexed(7).
  • Eliminating all diseases associated with pregnancy and parturition.
  • Eliminating the risk of developing tumours associated with the testes, ovaries or uterus (when ovariohysterectomy is undertaken).
  • Protecting against development of vaginal leiomyomas in female dogs(8) and reducing the risk of hepatoid gland adenomas in male dogs.
  • Preventing benign prostatic hyperplasia (BHP) and associated diseases (e.g. prostatitis, cysts, perineal herniation). BHP develops in half of all intact male dogs by five years of age(9).
  • Reducing injuries related to roaming and aggressive behaviours (e.g. traffic accidents and fight wounds(6)).
  • Male entire cats have a higher prevalence of feline immunodeficiency virus infection than de-sexed cats(10).
  • Providing protection against the risk of developing mammary tumours in female cats and dogs if de-sexed before the third oestrus cycle. The highest level of protection was achieved in those cats and dogs de-sexed pre-pubertally. The evidence for this protective effect was reviewed in 2012 and found to weakly support this benefit (11).

De-sexing cats and dogs will also provide benefits to their owners:

  • Cats and dogs are less likely to require expensive treatment for injuries related to roaming and fighting.
  • Eliminating undesirable behaviours associated with hormonal cycling in female cats and dogs (e.g. attracting other cats and dogs to the house, vaginal bleeding and “calling cats”).
  • Male cats and dogs display reduced urine marking in the house, humping, and roaming behaviours (12).
  • Council registration fees for de-sexed dogs are often lower.
  • Unpleasant odours associated with male cats are eliminated.
  • Admission to doggy day-care facilities, boarding kennels and catteries usually require cats and dogs to be de-sexed.

Negative effects associated with de-sexing


Obesity is a major health problem in companion cats and dogs in New Zealand. De-sexing cats and dogs has been associated with reduced metabolic rates and weight gain (13). The risk of weight gain is not a contraindication to de-sexing as it can be simply managed. Owners should receive nutritional counselling prior to their pet being de-sexing. Owners must understand the changed food intake requirements for their pets and how to manage their pet’s weight in the long-term.

Cranial cruciate ligament rupture in large-breed dogs

There is evidence that suggests delaying de-sexing in large breed dogs, in particular golden retrievers, until after growth plates are closed may reduce the future risks of rupturing cranial cruciate ligaments(14) (15). Recommendations to delay de-sexing in individual dogs must be balanced with other considerations such as the owner’s ability to manage and train an intact dog, the potential for unwanted breeding, the increased risk of mammary gland neoplasia in female dogs, and the dangers to the dog from behaviour such as roaming and inter-dog aggression.

Urinary incontinence in female dogs

There is weak evidence that supports a possible link between urinary incontinence in de-sexed female dogs. The risk of incontinence may be higher in dogs that were de-sexed at a younger age (16). Delaying de-sexing until after 16-20 weeks of age, particularly in large breeds may reduce the risk of developing urinary incontinence (17). Treatment options exist for urinary incontinence and this condition is not considered a contraindication to de-sexing female dogs when weighed against the benefits of de-sexing.

Other relationships between neutering and disease in dogs

While de-sexing is well established to provide protection against some types of tumours, some studies have shown that de-sexing may mildly elevate the risk of developing some other types of tumours in susceptible dogs (18) (19) (14) (20) (21) (22) (23) (24) (25).

De-sexing has also been linked with:

  • problem behaviours in dogs (25, 26)
  • immune disorders in dogs (27)
  • feline lower urinary tract disease (28)
  • recessed or hypoplastic vulva in some dogs pre-pubertally de-sexed, predisposing to peri-vulvar dermatitis and cystitis
  • hip dysplasia in large breed dogs (14)

Associations reported between diseases and de-sexing do not necessarily indicate cause and effect, as many other factors such as age, genetics, environment, husbandry practices and body condition score also play a role.

Early age neutering (EAN)

This is commonly practiced in shelters primarily as a tool to manage overpopulation. Breeders may also request EAN prior to placing puppies or kittens in a new home. EAN also removes compliance issues associated with de-sexing voucher redemption schemes when rehoming or selling cats and dogs and has a positive impact on population management.

General guidelines for kittens and puppies undergoing EAN are that they should be over 8 weeks of age and weigh at least 1 kilogram, in addition to being in good general health. Attention to managing risks associated with hypoglycaemia and hypothermia, such as reducing pre-surgical fasting times to 3-4 hours and employing active warming systems is particularly important for paediatric anaesthesia.

Surgery on pre-pubertal animals is considered technically less demanding than those that are fully mature and associated with lower surgical complication rates and more rapid recovery (29).

Puppies and kittens are subjected to many events and situations that can cause stress in the first few weeks of their lives. This includes being exposed to viruses if kept in catteries or kennels, parasite burdens, weaning, vaccinations and disruptions associated with re-homing. Consideration to timing surgery to minimise the impact of this additional stressor should be given.

Public policy

To manage the negative welfare outcomes associated with unwanted cats and dogs, the NZVA would support a requirement that unowned animals are de-sexed prior to their sale or adoption from animal welfare organisations and animal control agencies.

The NZVA does not support regulations or legislation mandating de-sexing of privately owned, non-shelter dogs and cats. Mandatory approaches may contribute to pet owners avoiding registration, microchipping and veterinary care for their pets, and therefore may have other unintended consequences. The NZVA instead supports voluntary de-sexing, together with community education programmes to support responsible cat and dog ownership.


  1. De-sexing: a significant surgical procedure that removes the gonads
  2. Ovariohysterectomy: a significant surgical procedure removing both the ovaries and the uterus.
  3. Ovariectomy: a significant surgical procedure removing only the ovaries and not the uterus.
  4. Spay: de-sexing a female animal either by ovariohysterectomy or ovariectomy
  5. Castration: de-sexing a male by bilateral orchidectomy
  6. Neutering: de-sexing either a male or female animal
  7. Puberty: the age when sexual reproduction is possible
  8. Pre-pubertal: the age before puberty is attained
  9. Traditional age neutering – 6-9 months of age
  10. Early-age neutering – 8-16 weeks of age
  11. Pre-pubertal neutering: neutering prior to the onset of puberty


  1. Veterinary Taskforce on Feline Sterilization. Recommendations for age of spay and neuter surgery. Winn Feline Foundation. [Online] 2016.
  2. WSAVA Global Pain Council. Castration and ovariohysterectomy/ovariectomy: cats. [Online] 2014.
  3. WSAVA Global Pain Council. Castration and ovariohysterectomy/ovariectomy: dogs. [Online] 2014.
  4. Comparison of surgical variables and short-term postoperative complications in healthy dogs undergoing ovariohysterectomy or ovariectomy. Peeters, M.E. and Kirpensteijn, J. 2, 2011, Journal of the American Veterinary Medical Association, Vol. 238, pp. 189-194.
  5. Retrospective Analysis of the Learning Curve Associated With Laparoscopic Ovariectomy in Dogs and Associated Perioperative Complication Rates. Pope, J.F.A. and Knowles, T.G. 6, 2014, Veterinary Surgery, Vol. 43.
  6. Reproductive capability is associated with lifespan and cause of death in companion dogs. Hoffman, J.M., Creevy, K.E. and Promislow, D.E.L. 4, 2013, Vol. 8.
  7. A retrospective study of pyometra at five RSPCA hospitals in the UK: 1728 cases from 2006 to 2011. Gibson, A., et al. 16, 2013, The Veterinary Record, Vol. 173.
  8. Vulvar and vaginal tumors in the dog:a retrospective study. . Thacher, C. and Bradley, R.L. 6, 1983, Journal of the American Veterinary Medical Association, Vol. 183, pp. 690-692.
  9. Development of canine benign prostatic hyperplasia with age. Berry, S.J., et al. 4, 1986, Prostate, Vol. 9, pp. 363-373.
  10. Prevalence and risk factors for cats testing positive for feline immunodeficiency virus and feline leukaemia virus infection in cats entering an animal shelter in New Zealand. Gates, M.C., Vigeant, S. and Dale, A. 6, 2017, New Zealand Veterinary Journal, Vol. 65, pp. 285-291.
  11. Beauvais, W., Cardwell, J.M. and Brodbelt, D.C. The effect of neutering on the risk of mammary tumours in dogs – a systematic review. Journal of Small Animal Practice. 2012, Vol. 53, 6, pp. 314-322.
  12. Effects of castration on problem behaviors in male dogs with reference to age and duration of behavior. Neilson, J.C., Eckstein, R.A. and Hart, B.L. 2, 1997, Journal of the Americal Veterinary Association, Vol. 211, pp. 180-182.
  13. Fettman, M.J., et al. Effects of neutering on bodyweight, metabolic rate and glucose tolerance of domestic cats. Research in Veterinary Science. 1997, Vol. 62, pp. 131-136.
  14. Neutering dogs: Effects on joint disorders and cancers in golden retrievers. Torres de la Riva, G., et al. 2, 2013, PLoS ONE, Vol. 8.
  15. Risk factors for excessive tibial plateau angle in large-breed dogs. Duerr, F.M., et al. 11, 2007, Journal of the American Veterinary Medical Association, Vol. 231, pp. 1688-91.
  16. The effect of neutering on the risk of urinary incontinence in bitches – a systematic review. Beauvais, W, Cardwel, J.M. and Brodbelt, D.C. 4, 2012, Journal of Small Animal Practice, Vol. 53, pp. 198-204.
  17. Urethral Sphincter Mechanism Incompetence in 163 Neutered Female Dogs: Diagnosis, treatment, and relationship of weight and age at neuter to development of disease. Byron, J.K., et al. 2, 2017, Journal of Veterinary Internal Medicine, Vol. 31, pp. 442-448.
  18. Cooley, D.M., et al. Endogenous gonadal hormone exposure and bone sarcoma risk. Cancer Epidemiology, Biomarkers and Prevention. 2002, Vol. 11, 11, pp. 1434-1440.
  19. Bryan, J.N., et al. A population study of neutering status as a risk factor for canine prostate cancer. Prostate. 2007, Vol. 67, 11, pp. 1174-1181.
  20. Hormonal and sex impact on the epidemiology of canine lymphoma. Villamil, J.A., et al. 591793, 2009, Journal of Cancer Epidemiology, Vol. 2009.
  21. Cutaneous MCTs: associations with spay/neuter status, breed, body size, and phylogenetic cluster. White, C.R., et al. 3, 2011, Journal of the American Animal Hospital Association, Vol. 47, pp. 210-216
  22. Epidemiologic, clinical pathologic, and prognostic characteristics of splenic hemangiosarcoma and splenic hematoma in dogs. Prymak, C., et al. 6, 1988, Journal of the American Veterinary Medical Association, Vol. 193, pp. 706-712.
  23. Cardiac tumors in dogs:1982-1995. Ware, W.A. and Hopper, D.L. 2, 1999, Journal of Veteinary Internal Medicine, Vol. 13, pp. 95-103.
  24. Canine bladder and urethral tumors: a retrospective study of 115 cases (1980-1985). Norris, A.M., et al. 3, 1992, Journal of Veterinary Internal Medicine, Vol. 6, pp. 145-153.
  25. Evaluation of the risk and age of onset of cancer and behavioral disorders in gonadectomized Vizslas. Zink, M.C., et al. 3, 2014, Journal of the American Veteinary Medical Association, Vol. 244, pp. 309-319.
  26. Behavioural risks in male dogs with minimal lifetime exposure to gonadal hormones may complicate population-control benefits of desexing. McGreevy, P.D., et al. 5, 2018, PLoS ONE, Vol. 13.
  27. The association between acquired urinary sphincter mechanism incompetence in bitches and early spaying: A case-control study. de Bleser, B., et al. 1, 2016, The Veterinary Journal, Vol. 187.
  28. Epidemiologic study of risk factors for lower urinary tract diseases in cats. Lekcharoensuk, C., Osborne, C.A. and Lulich, J.P. 9, 2001, Journal of the American Veterinary Medical Association, Vol. 218, pp. 1429-1435.
  29. Early spay-neuter: clinical considerations. Kustritz., M.V. 3, 2002, Clinical Techniques in Small Animal Practice, Vol. 17.