Walk into any vets with an entire dog of any age and one of the first questions you will be asked is - "are you planning to have your dog castrated / bitch spayed?" There is an obsession amongst vets to sterilise dogs, which may originate from their endeavours to reduce the stray dog population. That argument may be true for latch-key dogs, but it is not the case for dogs kept secure by responsible owners, and sterilising for the sake of it or for socially accepted routine purposes may not be the panacea you expect.

We are often asked our opinions on whether people should have their pets spayed (F) or neutered (M). Our response is that it depends on the individual dog. Castrating males will take the edge off a highly sex driven dog. It will not necessarily stop aggressive dominance behaviours in the local park, especially if the dog has already learned to behave aggressively through sexual and territorial dominance. In a highly sex driven dog, it will, however, eliminate the production of testosterone and therefore enable such dogs to concentrate so the owner can train them. We once had a dog for training who was stick thin, marked continually and panted constantly. Poor dog couldn't even think straight but the owner (who was ball possessive!) couldn't see it would benefit his dog.

Young dogs showing mounting behaviour in the park and 'embarrassing their owners', is not a good enough reason to castrate.

There are many entire dogs who are very easy going, not highly sexed or confrontational who would not benefit in any way from being castrated and who could suffer other problems from castration. Unfortunately vets have a catch all policy, and don't take individuals into account. Neither do they take into account the adverse physiological consequences of spaying, notably orthopaedic with higher incidences of hip dysplasia and other cancers and we condemn vets employed by the RSPCA who are routinely sterilising puppies as early as 12 weeks.

There are no psychological changes to spayed bitches. The chances of pyometra (life threatening womb infection after season) are negated, but the chances of incontinence are significantly increased.

Thank you to the authors of the following articles who have given permission for me to reproduce their excellent, balanced, articles with solid statistics. You can then decide for yourself whether you proceed with sterilising your dog weighing up the benefits AND the drawbacks.


The following article by was originally published in Our Dogs paper and reproduced here by kind permission of the author

Jim Stephens
MSc. CABC Southampton
Companion Animal Behaviour Counsellor

The Unkindest Cut? As a behaviourist I am often asked by owners for advice as to whether they should neuter their dogs or bitches. The pro neutering lobby argue from ethical and health grounds that neutering of dogs will prevent unwanted pups and protect the dogs from serious health problems such as mammary tumours and testicular cancer. A lot of owners also look to castration and spaying as a solution to certain behaviour problems and many are advised that neutering will “calm” the dog.
Before reviewing the most up to date research, let’s just pause to consider some of the above: responsible owners do not let their dogs roam the streets to chance upon a mating opportunity. Shelters and welfare groups that carry out home checks on prospective owners to judge them as prospective responsible owners then in effect say 'yes we trust you to look after the dog in your care but we don’t trust you to control its reproductive behaviour'.  In terms of health, it is important to remember that humans also suffer from the cancers described above but we don’t routinely castrate men in the off chance that they will develop testicular cancer. As for behaviour being calmed by neutering the efficacy of such treatment very much depends upon what behaviours are hormonally controlled  and how much the learned component of behaviour is addressed by behaviour modification. As a rule of thumb, castration is most likely to be curative when the problem behaviour is sexually dimorphic. In other words, it is specific to, or more common in, one sex than the other. Males exhibit behaviours which are influenced by testosterone, such as scent marking, roaming away from home to find potential mates, inappropriate sexual behaviour, aggression towards other males, and sometimes competitive aggression towards humans. Even when castration is relevant, there is only a percentage chance that it will work. This varies from 90% for some problems, such as roaming to find potential mates, down to 50% for others such as inappropriate scent marking. This is because the male brain is programmed to display male behaviour by testosterone even before birth. If the accurate diagnosis of a problem shows that castration is likely to help, the chances of success are greatly improved if the operation is done in conjunction with behaviour modification therapy,
As a method of population control neutering is an irreversible solution, but only one method. Chemical castration is reversible and can be used to gauge whether behavioural changes are achievable before opting for irreversible surgery. Owner education and responsible ownership/ breeding are other methods of controlling the dog population.
Health benefits and risks of neutering
Welfare agencies and vets are often vociferous in proclaiming the health benefits of neutering  pointing to decreased rates of certain tumours in neutered dogs in relation to entire dogs. However, some of these rates require scrutiny : there is a difference between twice as likely to suffer from a potentially fatal disease which occurs often and a disease which is rare. Recent research into rates of disease make interesting reading . A summary of the Long-Term Health Risks and Benefits Associated with Spay / Neuter in Dogs carried out in 2007 found the following results :

“On balance, it appears that no compelling case can be made for neutering most male dogs, especially immature male dogs, in order to prevent future health problems. The number of health problems associated with neutering may exceed the associated health benefits in most cases.”

On the positive side, neutering male dogs
• eliminates the small risk (probably <1%) of dying from testicular cancer
• reduces the risk of non-cancerous prostate disorders
• reduces the risk of perianal fistulas
• may possibly reduce the risk of diabetes (data inconclusive)
On the negative side, neutering male dogs
• if done before 1 year of age, significantly increases the risk of osteosarcoma (bone cancer); this is a common cancer in medium/large and larger breeds with a poor prognosis.
• increases the risk of cardiac hemangiosarcoma by a factor of 1.6
• triples the risk of hypothyroidism
• increases the risk of progressive geriatric cognitive impairment
• triples the risk of obesity, a common health problem in dogs with many associated health problems
• quadruples the small risk (<0.6%) of prostate cancer
• doubles the small risk (<1%) of urinary tract cancers
• increases the risk of orthopaedic disorders such as hip dysplasia  and cranial ligament problems
• increases the risk of adverse reactions to vaccinations

For female dogs, the situation is more complex. The number of health benefits associated with spaying may exceed the associated health problems in some but not all  cases. On balance, whether spaying improves the odds of overall good health or degrades them depends on the age of the female dog and the relative risk of various diseases in the different breeds.

On the positive side, spaying female dogs
• if done before 2.5 years of age, greatly reduces the risk of mammary tumours, the most common malignant tumours in female dogs
• nearly eliminates the risk of pyometra, which otherwise would affect about 23% of intact female dogs; pyometra kills about 1% of intact female dogs
• reduces the risk of perianal fistulas
• removes the very small risk (_0.5%) from uterine, cervical, and ovarian tumours

On the negative side, spaying female dogs:
• if done before 1 year of age, significantly increases the risk of osteosarcoma (bone cancer); this is a
common cancer in larger breeds with a poor prognosis
• increases the risk of splenic hemangiosarcoma by a factor of 2.2 and cardiac hemangiosarcoma by a factor of >5; this is a common cancer and major cause of death in some breeds
• triples the risk of hypothyroidism
• increases the risk of obesity by a factor of 1.6-2, a common health problem in dogs with many associated health problems
• causes urinary “spay incontinence” in 4-20% of bitches
• increases the risk of persistent or recurring urinary tract infections by a factor of 3-4
• increases the risk of recessed vulva, vaginal dermatitis, and vaginitis, especially for female dogs spayed before puberty
• doubles the small risk (<1%) of urinary tract tumours
• increases the risk of orthopaedic disorders such as hip dysplasia  and cranial ligament problems
• increases the risk of adverse reactions to vaccinationsBehavioural effects of neutering.
It has long been held by vets, trainers and behaviourists that neutering helps reduce roaming, inappropriate mounting and urination and different forms of aggression especially male Interdog aggression and aggression directed towards owners, so called “dominance” aggression. New work in the last few years has looked retrospectively at some of this research and the results are very surprising.
One study found significant correlations between neutering dogs and increases in aggression, fear and anxiety, and excitability, regardless of the age at which the dog was neutered. There were also significant correlations between neutering and decreases in trainability and responsiveness to cues. The overall trend seen in these data was that the earlier the dog was neutered, the more negative the effect on the behaviour. This study has been supported by the work from the School of Veterinary Medicine, University of Pennsylvania whose large epidemiological study called into question generally held beliefs about the effects of spaying on dogs’ behaviour. Their results suggest that spayed female dogs tend to be more aggressive toward their owners and to strangers than intact females, but that these effects of spaying on behaviour appear to be highly breed-specific. Contrary to popular belief, the study found little evidence that castration was an effective treatment for aggressive behaviour in male dogs, and may even exacerbate other behavioural problems such as excessive licking, Not unnaturally where confidence is related to hormone levels, neutered dogs were found to be more fearful and anxious often with increased sensitivity to touch.

So what can we tell owners when they ask for advice ?  The best option is to give them both the pros and cons so that they can make a rational choice.

The balance of long-term health risks and benefits of spay/neuter will vary from one dog to the next. Breed, age, and gender are variables that must be taken into consideration in conjunction with non-medical factors such as owner expectations and circumstances for each individual dog. Across-the-board recommendations for all pet dogs to be neutered  do not appear to be supportable from findings in the veterinary medical literature. Given that a large percentage of dogs are surrendered to welfare agencies on behavioural and health grounds it would be unfortunate for all involved if these same agencies were in fact inadvertently adding to the problem of abandonment. For more details and  information on breeds most affected see:
:Long-Term Health Risks and Benefits Associated with Spay / Neuter in Dogs
Laura J. Sanborn, M.S .
Non-reproductive Effects of Spaying and Neutering on Behavior in Dogs Deborah L. Duffy, Ph.D., and James A. Serpell, Ph.D., Center for the Interaction of Animals and Society, School of Veterinary Medicine, University of Pennsylvania Proceedings of the Third International Symposium on Non-Surgical Contraceptive Methods for Pet Population Control •
Behavioral and Physical Effects of Spaying and Neutering Domestic Dogs (Canis familiaris) Parvene Farhoody


Early Spay-Neuter Considerations
for the Canine Athlete
One Veterinarian's Opinion
© 2005 Chris Zink DVM, PhD, DACVP

Those of us with responsibility for the health of canine athletes need to continually read and evaluate new scientific studies to ensure that we are taking the most appropriate care of our performance dogs. This article provides evidence through a number of recent studies to suggest that veterinarians and owners working with canine athletes should revisit the standard protocol in which all dogs that are not intended for breeding are spayed and neutered at or before 6 months of age.
Orthopedic Considerations
A study by Salmeri et al in 1991 found that bitches spayed at 7 weeks grew significantly taller than those spayed at 7 months, who were taller than those not spayed (or presumably spayed after the growth plates had closed).(1) A study of 1444 Golden Retrievers performed in 1998 and 1999 also found bitches and dogs spayed and neutered at less than a year of age were significantly taller than those spayed or neutered at more than a year of age.(2) The sex hormones, by communicating with a number of other growth-related hormones, promote the closure of the growth plates at puberty (3), so the bones of dogs or bitches neutered or spayed before puberty continue to grow. Dogs that have been spayed or neutered well before puberty can frequently be identified by their longer limbs, lighter bone structure, narrow chests and narrow skulls. This abnormal growth frequently results in significant alterations in body proportions and particularly the lengths (and therefore weights) of certain bones relative to others. For example, if the femur has achieved its genetically determined normal length at 8 months when a dog gets spayed or neutered, but the tibia, which normally stops growing at 12 to 14 months of age continues to grow, then an abnormal angle may develop at the stifle. In addition, with the extra growth, the lower leg below the stifle likely becomes heavier (because it is longer), and may cause increased stresses on the cranial cruciate ligament. In addition, sex hormones are critical for achieving peak bone density.(4) These structural and physiological alterations may be the reason why at least one recent study showed that spayed and neutered dogs had a higher incidence of CCL rupture.(5) Another recent study showed that dogs spayed or neutered before 5 1/2 months had a significantly higher incidence of hip dysplasia than those spayed or neutered after 5 1/2 months of age, although it should be noted that in this study there were no standard criteria for the diagnosis of hip dysplasia.(6) Nonetheless, breeders of purebred dogs should be cognizant of these studies and should consider whether or not pups they bred were spayed or neutered when considering breeding decisions.
Cancer Considerations
A retrospective study of cardiac tumors in dogs showed that there was a 5 times greater risk of hemangiosarcoma, one of the three most common cancers in dogs, in spayed bitches than intact bitches and a 2.4 times greater risk of hemangiosarcoma in neutered dogs as compared to intact males.(7) A study of 3218 dogs demonstrated that dogs that were neutered before a year of age had a significantly increased chance of developing bone cancer.(8) A separate study showed that neutered dogs had a two-fold higher risk of developing bone cancer.(9) Despite the common belief that neutering dogs helps prevent prostate cancer, at least one study suggests that neutering provides no benefit.(10) There certainly is evidence of a slightly increased risk of mammary cancer in female dogs after one heat cycle, and for increased risk with each subsequent heat. While about 30 % of mammary cancers are malignant, as in humans, when caught and surgically removed early the prognosis is very good.(12) Luckily, canine athletes are handled frequently and generally receive prompt veterinary care.
Behavioral Considerations
The study that identified a higher incidence of cranial cruciate ligament rupture in spayed or neutered dogs also identified an increased incidence of sexual behaviors in males and females that were neutered early.(5) Further, the study that identified a higher incidence of hip dysplasia in dogs neutered or spayed before 5 1/2 months also showed that early age gonadectomy was associated with an increased incidence of noise phobias and undesirable sexual behaviors.(6) A recent report of the American Kennel Club Canine Health Foundation reported significantly more behavioral problems in spayed and neutered bitches and dogs. The most commonly observed behavioural problem in spayed females was fearful behavior and the most common problem in males was aggression.(12)
Other Health Considerations
A number of studies have shown that there is an increase in the incidence of female urinary incontinence in dogs spayed early (13), although this finding has not been universal. Certainly there is evidence that ovarian hormones are critical for maintenance of genital tissue structure and contractility.(14, 15) Neutering also has been associated with an increased likelihood of urethral sphincter incontinence in males.(16) This problem is an inconvenience, and not usually life-threatening, but nonetheless one that requires the dog to be medicated for life. A health survey of several thousand Golden Retrievers showed that spayed or neutered dogs were more likely to develop hypothyroidism.(2) This study is consistent with the results of another study in which neutering and spaying was determined to be the most significant gender-associated risk factor for development of hypothyroidism.(17) Infectious diseases were more common in dogs that were spayed or neutered at 24 weeks or less as opposed to those undergoing gonadectomy at more than 24 weeks.(18) Finally, the AKC-CHF report demonstrated a higher incidence of adverse reactions to vaccines in neutered dogs as compared to intact.(12)
I have gathered these studies to show that our practice of routinely spaying or neutering every dog at or before the age of 6 months is not a black-and-white issue. Clearly more studies need to be done to evaluate the effects of prepubertal spaying and neutering, particularly in canine athletes.

Currently, I have significant concerns with spaying or neutering canine athletes before puberty. But of course, there is the pet overpopulation problem. How can we prevent the production of unwanted dogs while still leaving the gonads to produce the hormones that are so important to canine growth and development? One answer would be to perform vasectomies in males and tubal ligation in females, to be followed after maturity by ovariohysterectomy in females to prevent mammary cancer and pyometra. One possible disadvantage is that vasectomy does not prevent some unwanted behaviors associated with males such as marking and humping. On the other hand, females and neutered males frequently participate in these behaviors too. Really, training is the best solution for these issues. Another possible disadvantage is finding a veterinarian who is experienced in performing these procedures. Nonetheless, some do, and if the procedures were in greater demand, more veterinarians would learn them.

I believe it is important that we assess each situation individually. For canine athletes, I currently recommend that dogs and bitches be spayed or neutered after 14 months of age.

Salmeri KR, Bloomberg MS, Scruggs SL, Shille V.. Gonadectomy in immature dogs: effects on skeletal, physical, and behavioral development. JAVMA 1991;198:1193-1203
Grumbach MM. Estrogen, bone, growth and sex: a sea change in conventional wisdom. J Pediatr Endocrinol Metab. 2000;13 Suppl 6:1439-55.
Gilsanz V, Roe TF, Gibbens DT, Schulz EE, Carlson ME, Gonzalez O, Boechat MI. Effect of sex steroids on peak bone density of growing rabbits. Am J Physiol. 1988 Oct;255(4 Pt 1):E416-21.
Slauterbeck JR, Pankratz K, Xu KT, Bozeman SC, Hardy DM. Canine ovariohysterectomy and orchiectomy increases the prevalence of ACL injury. Clin Orthop Relat Res. 2004 Dec;(429):301-5.
Spain CV, Scarlett JM, Houpt KA. Long-term risks and benefits of early-age gonadectomy in dogs. JAVMA 2004;224:380-387.
Ware WA, Hopper DL. Cardiac tumors in dogs: 1982-1995. J Vet Intern Med 1999 Mar-Apr;13(2):95-103
Cooley DM, Beranek BC, Schlittler DL, Glickman NW, Glickman LT, Waters D, Cancer Epidemiol Biomarkers Prev. 2002 Nov;11(11):1434-40
Ru G, Terracini B, Glickman LT. Host related risk factors for canine osteosarcoma. Vet J. 1998 Jul;156(1):31-9.
Obradovich J, Walshaw R, Goullaud E. The influence of castration on the development of prostatic carcinoma in the dog. 43 cases (1978-1985). J Vet Intern Med 1987 Oct-Dec;1(4):183-7
Meuten DJ. Tumors in Domestic Animals. 4th Edn. Iowa State Press, Blackwell Publishing Company, Ames, Iowa, p. 575
Stocklin-Gautschi NM, Hassig M, Reichler IM, Hubler M, Arnold S. The relationship of urinary incontinence to early spaying in bitches. J. Reprod. Fertil. Suppl. 57:233-6, 2001
Pessina MA, Hoyt RF Jr, Goldstein I, Traish AM. Differential effects of estradiol, progesterone, and testosterone on vaginal structural integrity. Endocrinology. 2006 Jan;147(1):61-9.
Kim NN, Min K, Pessina MA, Munarriz R, Goldstein I, Traish AM. Effects of ovariectomy and steroid hormones on vaginal smooth muscle contractility. Int J Impot Res. 2004 Feb;16(1):43-50.
Aaron A, Eggleton K, Power C, Holt PE. Urethral sphincter mechanism incompetence in male dogs: a retrospective analysis of 54 cases. Vet Rec. 139:542-6, 1996
Panciera DL. Hypothyroidism in dogs: 66 cases (1987-1992). J. Am. Vet. Med. Assoc., 204:761-7 1994
Howe LM, Slater MR, Boothe HW, Hobson HP, Holcom JL, Spann AC. Long-term outcome of gonadectomy performed at an early age or traditional age in dogs. J Am Vet Med Assoc. 2001 Jan 15;218(2):217-21.


Thank you to Mary Wakeman DVM for allowing us to reproduce her article originally featured in BREEDERVET (US) magazine.


Politically correct conventional wisdom is not necessarily biologically correct. Also, old wives tales regarding testicles and behavioral matters are often just that.

The only true justifications for castrating dogs are 1) aggressive behavior toward other dogs in the same household, and 2) perianal adenoma in old dogs.

Aggression to other dogs in situations outside the house is pretty normal dog behavior. Appropriate behavior. Since your dog will be on lead or inside a secure fence at all times, there should be no problem with dogs outside your household. However, if male house mates fight, and both need to stay with you, castration of one or both may solve the aggression problems. If you fault your dog for being aggressive to acquaintances while being walked on lead, you should not. He is guarding you. That simple. Honorable behavior. If you fault your dog for aggression in a 'dog park' where he is running free, or on the beach, or in the woods, well shame on you; you're the one at fault for risking his life in such an uncontrolled situation. Dogs that can manage such encounters without aggression are fine, but you cannot automatically expect a dog to have friendly relations with animals from outside his own 'pack'. It goes against his whole evolution.

Perianal adenomas, benign but messy tumors in old dogs may be treated by castration.

In terms of your dog's health, two overriding concerns are present. Castration at an early age will cause the dog to become overly tall, as the growth plates in the long bones will not close at the appropriate time; additionally, the dog will lack breadth of chest. The combination of these two factors sets the stage for your dog to have painful orthopedic problems. The OFA has published articles on this subject. An early age means below 1 year in small and medium sized dogs, and below 2 to 2.5 years in large and giant breeds.

The statement that your dog will not automatically gain weight is rubbish. Removing sexual hormones will change his metabolism and make your dog more sluggish, resulting almost inevitably in weight gain. Also, muscle tone will decline after castration, and the classic result of this is a fat dog in poor muscle tone that ends up having a cruciate ligament rupture in the knee. Can you avoid the consequences to weight and condition? Sure in the ideal world it's possible, but in the real world, the overwhelming proportion of owners do not succeed in this endeavor.

The second concern regarding your dog's health is highly malignant prostate cancer. Virtually all malignant prostatic tumors in dogs occur in castrated dogs. Castrating your dog puts him at risk for one of the worst cancers he can get. While you remove the very slight risk of testicular cancer in castrated dogs, that's a small matter; the incidence of testicular cancer is so minimal. Also, almost all testicular cancers in dogs are benign. If we find a testicular tumor, we normally remove the testicle with the mass and leave the remaining one intact. The relative incidence and severity of the tumors of the prostate relative to tumors of the testicle makes the decision to keep your dog intact a virtual no-brainer. The information on the incidence prostatic malignancies was obtained through a very large study of the records at veterinary colleges. These findings have been published for several years.*

Infection or inflammation of the prostate may occur in intact male dogs that are chronically exposed to bitches in heat. These are often worrisome to owners who seem to confuse prostatitis with the more serious prostate cancer. Prostatic infections are easily treated, and not, per se, a reason for castration.

So, the bottom line is:
1. Never castrate your dog because it is Politically Correct
2. Only castrate your dog if his home life is at risk due to dog-to-dog
aggression, or if, at the age of 11 years or so, he develops a perianal adenoma. Mary C. Wakeman, D.V.M.
©2003 for BREEDERVET

All text and images Copyright Aritaur Dobermanns.