Spay/Neuter: When, not Why

In typical fashion, I am going to start with a caveat:  unless you are planning to breed your dog, yes, you should absolutely have him or her neutered/spayed.  It’s simply the responsible thing to do in order to help curb the population of unwanted pets and “oopsie” litters; we should leave the breeding up to responsible, educated breeders.  And with initiatives such as Calgary’s new no-cost spay/neuter program, there are fewer and fewer excuses to be made.

In fact, since we have decided to officially abandon our breeding aspirations for Moses (and end his unfruitful show career), at 2 ½ years old he’s going in for the ol’ snip-snip in a couple of days (with breeder consent, of course).

So the question is not if you should get your dog (or cat) fixed – Bob Barker had that right the whole time.  But there is a considerable debate about when: as young and soon as possible?  At 6 months?  After a year?  For females, after her first heat?  For males, a month after they start to lift their legs to pee?  Personally, I was always told that, especially for males, the larger the breed, the longer you should wait (18 months, barring any serious behavioural challenges); is that actually beneficial?

The traditional vet recommendation was always 6-9 months, but as it turns out, there is actually no scientific or medical reasoning for this figure aside from the fact that it’s generally just before the age of sexual maturity.  And, these days, early spaying and neutering is becoming more and more common.  And that’s what I want to discuss.

Early/Pediatric/Prepubertal Neutering

Means: spaying or neutering between 7 and 16 weeks old (provided the animal weighs more than two pounds and, for males, both testicles have dropped).

The Good

The number one benefit to early spaying and neutering is clearly population control.  While vets and commercial pets stores seem to be just getting into this trend, rescue agencies have been performing pediatric spaying and neutering much longer.  Because the compliance with post-adoption spay/neuter schedules and contracts for rescue animals is often lower than 40%, upwards of 60% of rescue adoptions never get fixed.  And no matter how watchful an owner may be, an accidental litter is always a possibility with an intact dog.  So, to prevent this, many rescues spay and neuter all pets before adopting them out.  This is simply pragmatic from a rescue point of view, and it is unreasonable to expect shelters to house animals until they reach 6 months/one year/18 months/whatever in order to fix them and then adopt them out.  Simply put, prepubertal neutering is a useful and effective way to prevent pet overpopulation.

In addition, early spaying and neutering may come with some physical and mental benefits.

Anaesthesia recovery in young animals is usually more rapid, with fewer complications.  Surgical complications are statically lowest for puppies neutered by 16 weeks.

Spaying females before the first heat nearly eliminates the risk of mammary (breast) cancer.  (However, I should note that another study suggests this risk is reduced as long as the spay is before the dog is 2.5 years old.) 

In addition, prepubertal spaying of female dogs prevents ovarian or uterine tumors.

A 2004 AVMA study showed that prepubertal spaying and neutering seems to play a role in reducing obesity – while all spayed/neutered pets as a whole are more overweight compared to their intact counterparts, the study shows that those spayed and neutered early were less so.

Other behavioural benefits include reduced separation anxiety, escaping behaviours, and inappropriate elimination (i.e. when frightened) in dogs that underwent pediatric spaying and neutering.

And generally, it is believed that for best behavioural results, it’s best not to wait past a year of age to neuter males, and many sources say early neutering of males is ideal to prevent potential aggressive and sexual behaviours.  This is because once a hormone-triggered behaviour has continued long enough, you can be dealing with a firmly entrenched habit that will not fade even after neutering (scent marking, for example).  Frequently, though, neutering at any age still helps with other types of behaviour problems often associated with intact males, and this behaviour result applies simply to neutering before sexual maturity, not within the 7-16 month period at issue.

The Bad

A handful of studies have shown that the traditional spay/neuter age of 6 months, as well as the modern practice of pediatric spay/neuter, appear to predispose dogs to health risks that could otherwise be avoided by waiting until the dog is physically mature, or perhaps in the case of many male dogs, foregoing it altogether unless medically necessary. 

AVMA researchers in June 2010 advised waiting until after 3 to 4 months of age to spay female dogs, finding more incidence of infectious disease in dogs neutered early as compared to dogs neutered at a traditional 6 month age.  Interestingly enough, they found no increased risk of disease or other health problems in cats neutered early.

Several studies have showed increased urinary incontinence/urinary tract infections in females spayed early, resulting in a similar recommendation to wait until at least 3 months of age to spay.  This is thought to be because females spayed before the onset of puberty are more likely to have a juvenile or recessed vulva.  Another study on this issue found that the risk increases the earlier the procedure is carried out, also recommending that female dogs be spayed no earlier than 3 to 4 months old.  I should note that a later study compared female dogs spayed between 4 to 6 months and after 6 months, and showed no increased risk between those two groups.  Incontinence, however, is often a major concern in most studies because it can be a lifelong condition requiring ongoing treatment.  The study even went so far as to say that this concern “may be particularly prudent for a shelter that does not have an excess of puppies and is focused on reducing medical and behavioural conditions that could lead to relinquishment of adolescent and adult dogs.  Conversely, for shelters with excess puppies, the advantages of [prepubertal spaying/neutering] of all dogs before adoption may outweigh the risk of urinary incontinence.”

A larger number of studies have shown early neutering (as early as 6 weeks) can lead to the growth of slightly longer legs and less “masculine” muscle development.  A 1991 study found that bitches spayed at 7 weeks grew significantly taller than those spayed at 7 months.  This is because sex hormones promote the closure of the growth plates at puberty, so the bones of dogs neutered or spayed before puberty continue to grow.  Therefore, 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.

A small number of uncontrolled studies have shown a link with early neuters (for these researchers, that meant before 14 months of age) and some forms of cancer and joint problems, with one citing that dogs neutered before one year old have a significantly increased risk (3 to 4 times more likely) of bone cancer, which is common in larger breed dogs.  According to one study, which combined the high breed risk with the increased early spay/neuter risk, Rottweilers spayed/neutered before one year old have a 28.4% (males) and 25.1% (females) risk of developing bone cancer.  This research suggests a cause-and-effect relationship, as sex hormones are known to influence the maintenance of skeletal structure and mass, and also because their findings showed an inverse relationship between time of exposure to sex hormones and risk of bone cancer.

In a study of beagles, surgical removal of the ovaries (as happens in spaying) caused an increase in the rate of remodelling of the pelvic bone, suggesting an increased risk of hip dysplasia with spaying.  Other studies have found that spaying/neutering before 5 ½ months of age is associated with a 70% increased aged-adjusted risk of hip dysplasia compared to dogs spayed/neutered after 5 ½ months of age, though there were some indications that the former may have had a lower severity manifestation of the disease.  It is suggested that neutering a giant breed male dog early (6 months for example), rather than at 18 months to two years, can almost ensure the dog will have structural or joint problems fully manifested by age six or seven years.  Yet another study has showed the incidence of hip dysplasia increased to 6.7% for dogs neutered before 5 ½ months compared to 4.7% for dogs neutered after 5 ½ months.

Spaying was also found to cause a net loss of bone mass in the spine.  Because the spay/neuter of immature dogs delays the closure of the growth plates in bones that are still growing, those bones end up significantly longer than those in intact dogs or those who are spayed/neutered after maturity.  Since the growth plates in various bones close at different times, spaying and neutering that is done after some growth plates have closed, but before other growth plates have closed, may result in a dog with unnatural proportions, possibly impacting performance and long term durability of the joints.

In terms of behaviour, one study found aggression towards family members actually more frequent among male dogs neutered before 5 ½ months, and prepubertal neutering was associated with higher rates of barking or growling at visitors and excessive barking that bothered household members. However, for dogs in the study that were not determined to have any aggression issues, there was no association between the ages of neutering and excessive barking.

It should also be noted that many dog professionals suggest that beyond the age of three is when the most trouble occurs in a non-neutered male. The high testosterone levels and hormonal changes in the male dog at three years of age often builds up, causing territorial and aggressive traits, so for behavioural concerns, this should be the longest one should wait.

The Possible

There are a number of unfounded claims out there that neutering a male dog before 2 years old will affect his “working ability”.  Though there seems to be nothing to actually prove this, and no reasoning I could find behind it, many sources still recommended that for “working” or “athletic” dogs to hold off spaying or neutering until about 14 months old.

My best guess is that this has to do with testosterone, which is the hormone responsible for the different physical and mental (and sexual) characteristics males tend to have in abundance (and females less so).  It promotes sex drive, fat loss, helps with gaining and maintaining lean muscle mass and bone density, most of which can be important physical considerations for the owners of working dogs.

Some trainers and behaviourists also have concerns about mental development of dogs that are spayed or neutered to early, in that they do not psychologically or behaviourally mature, and retain many puppy behaviours.  However, these seemed to be mostly based on personal experiences and hypotheses, with no actual studies performed or cited.

The Pitfalls

When researching this subject I found that while there seemed to be many sources, it turned out that people were just quoting the same handful of studies – often verbatim.  This signalled to me that no position is solidified when it comes to health benefits and concerns regarding prepubertal spaying and neutering.  Basically, more (and more long-term) research should be done.

The End

Despite the potential for concern, the American Animal Hospital Association takes an official position in support of “the concept of neutering cats and dogs as young as 8 weeks of age in order to help reduce the overpopulation problems in companion animals”.

And quite frankly, for many the overarching concern of unwanted pets and rescue animals is simply enough to promote early spaying and neutering in animals.  I do not disagree with this sentiment.

However, for individual owners of commercially purchased or breeder bought pets, I encourage them to look into the issue and decide for themselves based on their dog, its breed, its lineage and health history, and any vet recommendations.

Personally, as the owner of a giant-breed dog that is already at a decent risk of joint issues and hip dysplasia, I will not get my dog (or future dogs, I suppose) spayed or neutered early – and probably not until the 18 month mark at the earliest (barring any exceptional health or behavioural issue).  Even a slight increased risk in bone or joint issues is enough to deter me, and I would recommend the same for any other large- or giant-breed dog owners who ask.

In the end, I came across this conclusion which I think sums up my official position quite perfectly:

Animals housed at humane societies [and other rescue organizations] should be treated as a population.  Societal benefit resulting from [prepubertal spaying and neutering] of unowned dogs and cats … outweighs all other concerns.  Male and female dogs and cats should be spayed or castrated before being offered for adoption by humane organizations.

Pets should be considered individually, with the understanding that for these pets, population control is a less important concern than is health of each animal.  Dogs and cats should be maintained as household pets.  Responsible owners should ensure that their pets are provided appropriate and regularly scheduled veterinary care.

Sources, References, and Further Reading

Responsible Dog Ownership: Spaying and Neutering 

Long Term Health Risks and Benefits Associated with Spay/Neuter in Dogs:

The Controversy is Over: Prepubertal Neutering is the Surgery of Choice:

Long-term risks and benefits of early-age gonadectomy in dogs:

Determining the optimal age for gonadectomy of dogs and cats: