Evaluating Risks and Benefits of Neutering Dogs and Cats

In response to questions from clients, and a lot of myths embedded in them, I set about last year reviewing the literature concerning the risks and benefits of neutering dogs and cats. This led to a handout for owners, which is available here. When this came out, I got some encouragement to produce a formal literature review for vets on the subject, and this has just been released in the online journal CAB Reviews. For those of you interested and with access to the journal, the article can be found here:

Evaluating the benefits and risks of neutering dogs and cats
CAB Reviews: Perspectives in Agriculture, Veterinary Science, Nutrition and Natural Resources 2010 5, No. 045

Abstract

Neutering consists of removing the source of the hormones that control reproduction and determine secondary sexual characteristics. In dogs and cats, this is most commonly accomplished by castration or ovariectomy. While the primary purpose of neutering is to prevent reproduction, the procedure may have other physical and behavioural effects.

Epidemiologic research has identified many beneficial and harmful outcomes associated with neutering. A definitively causal relationship between these outcomes and neuter status cannot be accepted without consistent evidence from multiple studies of adequate size and quality. However, consideration of the possible health consequences of these associations is warranted when offering owners recommendations concerning neutering.

An evidence-based decision about neutering a particular pet requires integrating relevant research data with the veterinarian’s clinical expertise and the needs and circumstances of the patient and owner. It is impossible to precisely predict the outcome of neutering for any individual. However, existing research does allow some generalization about the magnitude and clinical importance of specific risks and benefits. Overall, it appears justified to recommend spaying all females not intended for breeding, because the procedure is more likely to prevent rather than cause disease. In male dogs, the benefits of castration are not so clearly greater than the risks. The evidence is also mixed regarding the risks and benefits of neutering dogs before 5–6 months of age, and so no strong recommendation for or against the practice can be made. However, it is clear that spaying female dogs before their first heat is preferable to spaying them later.

This entry was posted in Science-Based Veterinary Medicine. Bookmark the permalink.

21 Responses to Evaluating Risks and Benefits of Neutering Dogs and Cats

  1. It will be interesting to see if someone comes up with a formula that you can plug in how longer you wait to remove ovaries and how much longer the formula estimates your pet will live. Many vets in europe have the opinion you need a existing behavioral or medical reason to remove body parts.

    A Healthier Respect for Ovaries
    David J. Waters, DVM, PhD, Diplomate ACVS

    A recent study by my research group appearing next month in Aging Cell reveals shortened longevity as a possible complication associated with ovary removal in dogs (1). This work represents the first investigation testing the strength of association between lifetime duration of ovary exposure and exceptional longevity in mammals. To accomplish this, we constructed lifetime medical histories for two cohorts of Rottweiler dogs living in 29 states and Canada: Exceptional Longevity Cohort = a group of exceptionally long-lived dogs that lived at least 13 years; and Usual Longevity Cohort = a comparison group of dogs that lived 8.0 to 10.8 years (average age at death for Rottweilers is 9.4 years). A female survival advantage in humans is well-documented; women are 4 times more likely than men to live to 100. We found that, like women, female Rottweilers were more likely than males to achieve exceptional longevity (Odds Ratio, 95% confidence interval = 2.0, 1.2 – 3.3; p = .006). However, removal of ovaries during the first 4 years of life erased the female survival advantage. In females, this strong positive association between ovaries and longevity persisted in multivariate analysis that considered other factors, such as height, adult body weight, and mother with exceptional longevity.

    In summary, we found female Rottweilers who kept their ovaries for at least 6 years were 4.6 times more likely to reach exceptional longevity (i.e. live >30 % longer than average) than females with the shortest ovary exposure. Our results support the notion that how long females keep their ovaries determines how long they live.

    In the pages that follow, I have attempted to frame these new findings in a way that will encourage veterinarians to venture beyond the peer-reviewed scientific text and data-filled tables of Aging Cell to consider the pragmatic, yet sometimes emotionally charged implications of this work. Call it a primer for the dynamic discussions that will undoubtedly take place, not only between practitioners and pet owners, but also within the veterinary profession. Call it a wake-up call for how little veterinarians have been schooled in the mechanistic nuts and bolts underlying the aging process. Call it an ovary story.

    Do ovaries really promote longevity? Observed associations between exposures and outcomes may not necessarily be causal, so we explored alternative, non-causal explanations for the association between ovaries and exceptional longevity in our study. But we found no evidence that factors which may influence a pet owner’s decision on age at ovary removal — for example, earlier ovariectomy in dogs with substandard conformation or delayed ovariectomy to obtain more offspring in daughters of long-lived mothers — could adequately account for the strong association.

    There is another aspect of our data pattern that gives us further confidence that ovaries really do matter when it comes to successful aging. A simple explanation for the observation that ovaries promote longevity would be that taking away ovaries increases the risk for a major lethal disease. In Rottweilers, cancer is the major killer. We found, however, that by conducting a subgroup analysis that excluded all dogs that died of cancer, the strong association between intact ovaries and exceptional longevity persisted. After excluding all cancer deaths, females that kept their ovaries the longest were 9 times more likely to reach exceptional longevity than females with shortest ovary exposure. Thus, we observed a robust ovarian association with longevity that was independent of cause of death, suggesting that a network of processes regulating the intrinsic rate of aging is under ovarian control. This work positions pet dogs, with their broad range of lifetime ovary exposure, to become biogerontology’s new workhorse for identifying ovary-sensitive physiological processes that promote healthy longevity.

    Interestingly, our findings in dogs surface just as data from women are calling into question whether those who undergo hysterectomy should have ovary removal or ovary sparing. In fact, our results mirror the findings from more than 29,000 women in the Nurses’ Health Study who underwent hysterectomy for benign uterine disease (2). In that study, the upside of ovariectomy — protection against ovarian, uterine, and breast cancer — was outweighed by increased mortality from other causes. As a result, longevity was cut short in women who lost their ovaries before the age of 50 compared with those who kept their ovaries for at least 50 years. Taken together, the emerging message for dogs and women seems to be that when it comes to longevity, it pays to keep your ovaries.

    But before we all go out and buy T-shirts with some romantic imperative like “Save the Ovaries”, perhaps we should step back and consider the following question: Why haven’t previous dog studies called our attention to this potential downside of ovariectomy? Reviewing the literature, an answer quickly bubbles up. No previous studies in pet dogs have rigorously evaluated the association between ovaries and longevity. Two frequently cited reports (3,4) provide limited guidance because: (1) longevity data are presented as combined mean age at death for a relatively small number of individuals of more than 50 breeds of different body size and life expectancy; and (2) ovarian status is reported as “intact” or “spayed”, rather than as number of years of lifetime ovary exposure. Comparing female dogs binned into the categories of “intact” versus “spayed” introduces a methodological bias that might lead one to conclude that ovaries adversely influence longevity, i.e. ovary removal promotes longevity. Because the reasons for ovariectomy (e.g., uterine infection, mammary cancer) increase with increasing age, it is expected that a large percentage of the oldest-dogs are binned as “spayed” despite having many years of ovary exposure. For example, a dog who at age 12 undergoes ovariohysterectomy for pyometra would be binned as “spayed”, despite 12 years of ovary exposure. In our study, we employed a more stringent study design — restricting the study population to AKC registered, pure-bred dogs of one breed, carefully quantitating the lifetime duration of ovarian exposure — in order to lessen the likelihood of such bias. And we reasoned that studying veterinary teaching hospital-based populations of dogs with artifactually low life expectancies (for example, 3.5 years is median age at death for Rottweilers in the Veterinary Medical Data Base)(5) was an inappropriate vehicle to describe the influence that ovaries have on aging. So we cast a wider net and collected data from Rottweiler owners nationwide, focusing our attention on exceptional longevity, not average age at death, as our study endpoint.

    Why study exceptional longevity? Why not average longevity? We thought studying the most exceptionally long-lived individuals would tell us something about what it takes to age successfully. It’s the same rationale used by Thomas Perls and investigators of the New England Centenarian Study (6) and by other scientists who study long-lived humans in other parts of the world (7). The approach even garners support from the mathematical field. In a seminal book on the origins of creative genius, the mathematician Jacques Hadamard wrote: “In conformity with a rule which seems applicable to every science of observation, it is the exceptional phenomenon which is likely to explain the usual one.” (8) Hadamard was trying to understand how the brain gets creative so he studied people with extreme creativity. When it comes to studying aging, we’re solidly in the Hadamard camp. That is why in 2005 we established the Exceptional Longevity Data Base, launching the first systematic study of the oldest-old pet dogs (9). But folks in the opposing camp might justifiably fire back: “Don’t study extreme longevity. Extreme longevity is much more about luck than it is about genes, or environment, or ovaries.”

    So to address the possibility that the “strangeness” or outlier nature of dogs with exceptional longevity could be forging a misleading link between ovaries and longevity, we studied a separate cohort of Rottweiler dogs. This data set was comprised of 237 female Rottweilers living in North America that died at ages 1.2 to 12.9 years — none were exceptionally long-lived. Information on medical history, age at death, and cause of death was collected by questionnaire and telephone interviews with pet owners and local veterinary practitioners. In this population, we found females that kept their ovaries for at least 4.5 years had a statistically significant 37% reduction in mortality rate (1). This translated into a median survival of 10.4 years for females with more than 4.5 years of ovary exposure — 1.4 years longer than the median survival of only 9.0 years in females with shorter ovary exposure (p < 0.0001). Taken together, if you take out ovaries before 4 years of age you cut longevity short an average of 1.4 years and decrease the likelihood of reaching exceptional longevity by 3-fold.

    Up to this point, my ovary story has centered around a summarizing of methodologies and results. The reader has been given opportunity to see the gist of our findings within the context of previous dog studies and late-breaking studies in women. Now, let us pivot our attention a bit away from the results to focus on the recipients of these results — DVMs and pet owners.

    We can start by tackling the question: Just how receptive will DVMs be to these new research findings? It’s hard for old dogs to learn new tricks. But one thing is sure — blossoming change is rooted in real communication. The anthropologist Gregory Bateson wrote: “The pre-instructed state of the recipient of every message is a necessary condition for all communication. A book can tell you nothing unless you know 9/10ths of it already.” (10). I call this “Bateson’s Rule of the 9/10ths”. If Bateson is right, then we will want to do something about the pre-instructed state of veterinarians. Because when it comes to the biology of aging, the state is virtually a blank slate. None of us received training in the biology of aging as part of our DVM curriculum — whether we graduated 30 years ago or last summer. Therefore, most DVMs are ill-prepared to receive messages examining the mechanistic underpinnings of the aging process. A Batesonian prescription for positive change would be to ratchet up the biology of aging IQ of practicing veterinarians. We agree. That is why we established the first gerontology training program for veterinarians in 2007 (11). We believe that by helping veterinarians “know” more about aging, they will be more able and more receptive to communicating the things that promote healthy longevity in their patients — things like preserving ovaries.

    For certain, DVMs will be asked by pet owners to help them make their decision about age at spay in light of this new information. The question will be asked: Just how generalizable are these findings in Rottweilers to other segments of the pet dog population? It is impossible to say at this time. It will demand further study. Alas, 10 years from now, we might just find out that a longevity-promoting effect of ovaries in dogs is limited — limited to large breeds, urban but not rural dogs, or only those individuals with particular polymorphisms in insulin-like growth factor-1. These restrictions should not only be expected, they should be celebrated. It will mean that we have looked more deeply into how ovaries might influence healthy longevity. It will mean that our initial findings have been contextualized. And it is this contextualization of information that marks scientific progress — the kind of progress that guides sound clinical decision making. For it is context that determines meaning (12).

    Our provocative findings in Aging Cell mean that it’s time to re-think the notion that taking away ovaries has no significant downside to a dog’s healthy longevity. Perhaps it would help us if we thought of lifetime ovary exposure as information — information that instructs the organism. Just how long and how healthy a female lives reflects what her cells, tissues, and organs thought they heard from the message received. Of course in biology, there is no single message but a symphony of messages, enabling each individual to successfully respond to environmental challenges. Our findings suggest that ovaries orchestrate that symphony. Taking away ovaries in early or mid-life makes for muddled information, less than perfect music.

    Information muddling can ensnarl decision-making. Our research takes an important first step toward disentangling the thinking about ovaries and longevity. We must never be paralyzed by the incompleteness of our knowledge. Our knowledge will always be incomplete — subject to revision, primed for further inquiry. This uncertainty, although invigorating for the investigator, is often painful for the practitioner who seeks simple, fact-driven algorithms to guide his action. Just as scientists will be called upon to forge ahead with their scientific inquiries, so too will practitioners be counted on to master the uncertainty. Together, we must navigate what the Danish philosopher-theologian Soren Kierkegaard called the gap “between the understanding and the willing.” That is, we must ask the right questions and make smart choices so that our action (the willing) is in synch with our knowledge (the understanding). Under just what circumstances will a particular individual benefit from specific lifestyle decisions? This is perhaps the most prescient, overarching question in the wellness and preventive medicine fields facing both human and veterinary health professionals today. How can we promote healthy longevity? Antioxidant supplementation or calorie restriction? Ovary removal or ovary sparing?

    Undoubtedly, there will be protagonists and antagonists in this ovary story. The protagonists will be open-minded to following a new script. They will embrace the idea of ovary sparing for critical periods of time to maximize longevity. They might even recognize the need for some sort of “ovarian mimetic” in spayed dogs to optimize healthy aging. The antagonists in this story — the defenders of the old script — will dismiss as trivial the notion that ovaries regulate the rate of aging and influence healthy longevity. Lines will be drawn and opinions will fly. But that's what healthy debate is — antagonists and protagonists keeping a high priority issue front and center, not allowing it to fade into the woodwork. It would seem that, in light of the new scientific findings, a contemporary dialogue should balance the potential benefits of elective ovary removal (13) with its possible detrimental effects on longevity.

    References

    1. Waters DJ, Kengeri SS, Clever B, et al: "Exploring the mechanisms of sex differences in longevity: lifetime ovary exposure and exceptional longevity in dogs." Aging Cell October 26, 2009

    2. Parker WH, Broder MS, Chang E et al: "Ovarian conservation at the time of hysterectomy and long-term health outcomes in the Nurses' Health Study." Obstet Gynecol 113: 1027-1037, 2009

    3. Bronson RT: "Variation in age at death of dogs of different sexes and breeds." Am J Vet Res 43: 2057-9, 1982

    4. Michell AR: "Longevity of British breeds of dog and its relationships with sex, size, cardiovascular variables and disease." Vet Rec 145: 625-629, 1999

    5. Patronek GJ, Waters DJ, Glickman LT et al: "Comparative longevity of pet dogs and humans: implications for gerontology research." J Gerontol A Biol Sci Med Sci 52: B171-8, 1997

    6. Perls TT, Hutter Silver M, Lauerman JF: Living to 100: Lessons in Living to Your Maximum Potential at Any Age, New York, NY, Basic Books, 1999

    7. Franceschi C, Motta L, Valensin S et al: "Do men and women follow different trajectories to reach extreme longevity?" Aging (Milano) 12: 77-84, 2000

    8. Hadamard J: The Psychology of Invention in the Mathematical Field. New York, NY, Oxford Univ Press, 1945, p. 136

    9. Waters DJ, Wildasin K: "Cancer clues from pet dogs." Sci Am 295: 94-101, 2006

    10. Bateson G, Bateson MC: Angels Fear: Towards an Epistemology of the Sacred. New York, NY, Bantam, 1988, p 163

    11. Gerontology Program for DVMs co-sponsored and organized by Gerald P. Murphy Cancer Foundation, Purdue University Center on Aging and the Life Course, P&G Pet Care; for more information go to http://www.gpmcf.org

    12. Waters DJ, Chiang EC, Bostwick DG: "The art of casting nets: fishing for the prize of personalized cancer prevention." Nutr Cancer 60: 1-6, 2008

    13. Kustritz MV: "Determining the optimal age for gonadectomy of dogs and cats." J Am Vet Med Assoc 231: 1665-75, 2007

    art malernee dvm
    lic 1820

  2. v.t. says:

    I suppose if additional research shows promise, that might be good news for pets and pet owners.

    Yet, a rise in puppy mills, animal hoarders, overcrowded shelters will still be the end result. Is a 2-4 year extension of life worth the end result? Is the potential for increased reproductive cancer, pyometra and other health problems worth the risk for a large population? Quite the conundrum.

    Maybe we should be thinking of researching birth control instead.

  3. Yet, a rise in puppy mills, animal hoarders, overcrowded shelters will still be the end result.>>>>>

    Thats what I was taught and told my clients until I looked at the data for spay and neuter programs to see if they can even be measured as successful.

    Is a 2-4 year extension of life worth the end result?>>>>> It would be for my pets. It may not be worth it for the Politicians that run the spay and neuter programs in the USA.

    art malernee dvm

  4. skeptvet says:

    I would point out that the Rottweiler study has a number of problems that make broad conclusions about ovaries and longevity premature. And, in any case, total cause mortality and overall risks and benefits of neutering must be considered, which is a complex and imperfect calculus. While it is true that mandatory neutering has less of an impact on pet population than we’d hoped, and there are reasons why it may not be a good idea, there has also been a dramatic decline in euthanasias at shleters in the last 40 years, and some of this is attributable to an increase in the rates of neutering pets. Europe may very well accomplish the same goals in a different way, but cultural issues are involved too.

    I addressed this study a bit in the review:

    There is some suggestion in research on laboratory animals as well as retrospective epidemiologic studies of dogs and cats that neutered animals may live longer than intact animals, though the effect is not large or consistent across studies.[58-61,63,146,147] There has been one retrospective survey study of Rottweiler dogs which found an association between the length of time females remained intact and their odds of achieving exceptional longevity (defined as a lifespan ? 13years).[62] However, a previous survey study from the same population reported intact females lived an average of 7.5 years, compared to 9.8 years for spayed females.[71] The implications of these studies for other breeds or for any general relationship between lifespan and neuter status is not clear. Also, the possible effects of differences in the care neutered and intact animals receive, genetic factors, and many other variables have not been evaluated, which complicates any interpretation of differences in longevity. Therefore, no firm conclusions can be drawn about the effect of neutering on longevity.

    58. Michell AR. Longevity of British breeds of dog and its relationship with sex, size, cardiovascular variables, and disease. Veterinary Record 1999;145(22):625-9.

    59. Bronson RT. Variation in age at death of dogs of different sexes and breeds. American Journal of Veterinary Research 1982;43(11):2057-9.

    60. Moore GE, Burkman KD, Carter MN, Peterson MR. Causes of death or reasons for euthanasia in military working dogs: 927 cases (1993-1996). Journal of the American Veterinary Medical Association 2001;219(2):209-14.

    61. Drori D, Folman Y. Environmental effects on longevity in the male rat: exercise, mating, castration and restricted feeding. Experimental Gerontology 1976;11(1-2):25-32.

    62. Waters DJ, Kengeri SS, Clever B, Booth JA, Maras AH, Schlittler DL, et al. Exploring mechanisms of sex differences in longevity: lifetime ovary exposure and exceptional longevity in dogs. Aging Cell 2009;8(6):752-5.

    63. Waters DJ, Shen S, Glickman LT. Life expectancy, antagonistic pleiotropy, and the testis of dogs and men. Prostate 2000;1:43(4);272-7.

    71. Cooley DM, Beranek BC, Schlittler DL, Glickman NW, Glickman LT, Waters DJ. Endogenous gonadal hormone exposure and bone sarcoma risk. Cancer Epidemiology, Biomarkers, and Prevention 2002;11:1434-40.

    146. Kraft W. Geriatrics in canine and feline internal medicine. European Journal of Medical Research 1998;3:3-41.

    147. Greer KA, Canterberry SC, Murphy KE. Statistical analysis regarding the effects of height and weight on life span of the domestic dog. Research in Veterinary Science 2007;82:208-14.

  5. v.t. says:

    Art,

    I’m just curious, why the label, you’re painting a pretty wide brush for many advocates of spay/neuter who have no political agenda. Unless, you’re referring to the politics of *mandatory spay/neuter*, and if so, even then, those for and against have some pretty compelling arguments.

    How can spay/neuter not be a measurable success, at least in terms of pet overpopulation? How can early spay/neuter not be a measurable success in terms of reduced cancers, pyometra, reproductive organ issues?

    I don’t think a very large percentage of pet owners are ready to handle the potential consequences if we wait to spay/neuter at suggested ages based on limited studies.

    I’m certainly not arguing we shouldn’t strive to improve life expectancy for our pets, (we’ve come a long way in science, medicine already, albeit slow), but I think health, economical and ethical decisions must be considered before neglecting what we know to be effective and beneficial to the majority.

  6. Art,

    I’m just curious, why the label, you’re painting a pretty wide brush for many advocates of spay/neuter who have no political agenda. >>>>>

    I think most people support spay and neuter programs in the USA because they think they work. Thats why I supported them until I started talking to vets from Europe. Why government fund something that has not been shown in good clinical studies to be effective unless its funded as investigation studies to see if one can be developed that works?
    art malernee dvm

  7. Note that the Waters et al manuscript is open access

    http://www3.interscience.wiley.com/cgi-bin/fulltext/122588424/PDFSTART

    Spay and neuter has become a political football in my county

    In my county, spay and neuter is the law although it can be confusing just what the law says. The county does spay and neuter for free out of what is often jokingly called a Mobil spay wagon using tax payer dollars. The vet who does spay and neuter for animal care and control it is an old friend of mine who got rich and bored so went to work for animal care and control to help out. Clients come to me for spay and neuter and I try my best to give them informed consent. I give clients the option of having the county do spay and neuter it because it is cheaper. My friend is known to be a good surgeon. I still keep the animals i spay and neuter overnight so I can watch them and do overnight pain management but most pets do OK without a doctor there post op at night. I also give clients the option to wait until they have a medical or behavioral reason to spay and neuter like the vets in Europe think I should do. The problem with that option is many clients who wait to see if a problem developed that spay and neuter may help may not register the pet with the county when the vaccine tag fee for a unneutered pet is 100 dollars a year. County vaccination/tag registration rate has dropped not only in my practice but through out the county since spay and neuter programs and animal care and control reports more not less animals are being put down. There is now a long waiting list for the spay wagon. Maybe that is a good thing for our pets if they live longer the longer they keep their ovaries,
    art malernee dvm
    fla lic 1820

  8. Kim says:

    To Art Malernee DVM,
    Ever been out of this country Art? Many places in Europe dogs run the streets, overpopulation is a major problem. Other places in Europe have extremely strict breeding guidelines like: Potential breeding pair must be at a certain level in conformation AND sport competition, health tested and accepted by the breed club to be outstanding examples of the breed. Then only puppies that pass their criteria can be registered. If you do not abide by these rules, any puppy you produce will be refused by the breed club for registration. Hence, minimal overpopulation. These places also have much more responsible public than in the USA, the land of no consequences. AND, these places don’t use animals as ATM machines like here in the good ‘ol US. The AKC and UKC among other clubs REGISTER EVERY PUREBRED PUPPY PRODUCED IN PUPPYMILLS. Did you know that? Absolutely no thought is given to the quality of the dog, and, um…. isn’t that what the purpose of these breed clubs is supposed to be? Spaying and neutering is the only way to keep the population down, and every shelter and rescue group in this country is overflowing. And you’re anti spay and neuter? Take the bag off your head Art.

  9. Sarah says:

    Why does the spay/neuter argument have to be so black and white? If people are worried about pet overpopulation, why can’t there be a middle ground? Why not perform tubal ligations, partial hysterectomy (leaving the ovaries intact) or vasectomies for male dogs? I would think these surgeries would be much less invasive for the dogs and they have the benefit of keeping their sex organs for longevity.

  10. skeptvet says:

    Good questions! Overpopulation is only one of many issues, and while that can be controlled with tubal ligations and vasectomies, most of the others can’t.

    For Females: By far the biggest issues are mammary cancer and uterine infections, and both of these are very common and very dangerous conditions which can only be prevented by removal of the overies. In Europe, it is common to remove just the ovaries, which works just as well as removing both ovaries and uterus. Removing just the uterus, however, would not affect the mammary cancer problem, and it is no safer or less invasive than removing both uterus and ovaries. As for longevity, it really is still an unanswered question what role sex hormones play in that. Despite the Rottweiler std=udies, there are others which show neutered females live longer than intact females even if you don’ count mammary cancer and uterine infections, and if you do count them they absolutely are healthier. So which the hypothesis that keeping your ovaries might lead to living longer is worth exploring, it is just an unproven idea, and there is as much evidence against it as for it, so it isn’t a good reason to decide not to spay your dog.

    For males: The benefits of neutering are far less dramatic for males. If they have behavior problems, it will probably help. If not, and if the owner is responsible about preventing reproduction or has the dog vasectomized, then it is probably fine to leave them intact. And there is no evidence at all that intact males live longer (the Rottweiler studies only included females).

    As far as the invasiveness of the procedures themselves, this really isn’t as much of an issue as people think. All the studies agree that with proper technique and appropriate pain controol, the surgeries are all very safe and complications and extremely rare. If we increased the risk of any disease even a tiny bit by performing a surgery that left the pet intact, we would be doing far more harm than good if the only benefit was a small surgical incision.

    So I agree that the debate isn’t black and white, and the reason I wrote such a long article was that it is complicated and contains lots of grey areas.

  11. boxer says:

    In boxer bitches, spaying seems to produce incontinence in many many cases, and this is a very bad consecuence.

  12. skeptvet says:

    Any evidence that this is a greater risk in this breed than in others?

  13. Massimo D'Accordi says:

    Hi there,
    came across this blog after a webinar on pros and cons of neutering; I think
    a couple of recent EB reviews carried out by the Royal veterinary college should be usefully added to the discussion on this fascinating subject:
    Beauvais et al (2012a) The effect of neutering on the risk of mammary tumours in dogs –a systematic review. JSAP, 53, 314–322
    Beauvais et al (2012b) The effect of neutering on the risk of urinary incontinence in bitches – a systematic review. JSAP, 53, 198–204

  14. skeptvet says:

    Thank you for bringing these excellent articles to me attention! I was aware of the fact that very few studies looking at the mammary neoplasia risk, but my own review was narrative, not systematic, so the additional detailed analysis of bias risk is very helpful.

    I agree with the authors that some of the limitations of the review methods could affect the conclusions. It is not impossible that better quality evidence exists not published in English, for example. Hopefully, the publication of these reviews will stimulate others to come forward with any additional evidence the authors did not evaluate. And, of course, knowing that the existing evidence is weak does not give us the answer to the question. It simply requires us to proportion our cnfidece in our conclusions to the strength of the evidence. In this case, I would say there is still reason to think that neutering has a beneficial effect on mammary cancer risk, but that that conclusion deserves less confidence and should be presented with the appropriate acknowledgement that it is not based on strong evidence. I can’t wait to see if these authors, or others, move forward with the next logical step; developing better evidence to answer these questions.

    Thanks again!

  15. Lisa Fair says:

    There is a very interesting article on this subject written by Dr. Zink. It can be found on her website at http://www.caninesports.com/useful-info.html. There is much to consider with this issue and further research is needed.

  16. skeptvet says:

    The problem with Dr. Zink’s article is that it only cites research suggesting harm and does not discuss any research that found no effect or benefits to neutering. This is a complex subject, and we have to be careful to avoid one-sided discussions of it.

  17. Pingback: Bowmanville – Comfortably Numb? | heatherclemenceau

  18. Gail McLarnon says:

    Here is what I think. THe AVMA and the CVMA should get off their butts, and create a Cochrane like Institute that reviews research on this issue – particularly given that millions upon millions of these surgeries are done annually – and it is way past time to determine the impact of said surgeries.

    To fund this institute and future research $5 for every spay and neuter done by vets in the USA and Canada in one year alone would yield multi millions of dollars.

    In the interim there needs to be education of the veterinary community on recent research and on alternatives to full S or N.

    Or how about funding a Research Advisory Committee that can review proposed research -ie methodologies etc BEFORE the research starts to try to insure we get good research for our donated dollars to research. They can first answer the question what is the criteria where-in this research could be applicable across what spectrum of dogs? How usefull will the answer be? ETc Etc Etc

    How about vets truly offering up free literature on intact dogs? How to safeguard your female from breeding, what heat looks like. If there is an oops mating, what are your options 24hs 48hrs 72 hrs later? How often to examine, where to and why to examine and what you look for in intact animals. It is the owners decision in the end to S+N or to elect an alternative option – are Vets being trained in Laser surgery, vasectomies etc? Tubal ligations, uterine removal without ovarian removal.

    What are the breeds at high risk for HD and ED – and what you as an owner can do to minimize that risk and or the severity of the disease. Hemangiosarcomas, osteosarcomas, PRA, cataracts and the list goes on and on and on.

    One day I shall take a video of all the Mutts I see on the street with obvious gaiting problems quite remininscent of HD and ED – it is quite sad, not to mention the purebred dogs. At least we have some idea with the purebred dogs the incident rate of these polygenetic conditions.

    As a breeder and a lover and owner of dogs, I need to and want to make well informed decisions that put the welfare of my dog and my puppies at the forefront of the decision making process, irrespective of what any-ones political agenda might be vs a vs pet over population problems in the USA.

  19. skeptvet says:

    More research is absolutely needed. The Cochrane Collaboration has actually been lobbied for years to allow veterinarians to form a special interest group, but so far they are not willing. And while systematic reviews are growing exponentially (about 260 in 2013 compared to ~ 5 ten years earlier), this is still negligible compared to the more than 5,600 reviews from Cochrane alone, and the many hundreds more from other sources.

    The resources available in veterinary medicine are paltry. The largest private player, for example, is Zoetis, a former subsidiary of Pfizer. The Zoetis research budget for veterinary medicines was about $7 million in 2013. The comparable Pfizer budget was $6-7 billion, and that was a sharp decline from previous years. So while more research is certainly needed, funding it is not simple. The largest private granting source is the Morris Animal Foundation, which does fantastic work but can only fund a couple million dollars a year in research.

    And, of course, government funding, which is a major resource in human medicine, contributes almost nothing to companion animal research, and only a moderate amount to food animal and public health veterinary studies. Government also refuses to regulate veterinary medicine to any appreciable degree, since it is believed requiring FDA licensing for most therapies, for example, would raise costs to the point that more animals would go without care.

    So, I absolutely agree with you about the need both for more research and for synthesis of the existing evidence. I am in fact part of several efforts to accomplish this through the Evidence-based Veterinary Medicine Association, the Royal College of Veterinary Surgeons Knowledge arm, the Centre for Evidence-based Veterinary Medicine at the University of Nottingham, and others. And there is no doubt that improving the standard of care is not a priority for the AVMA or most other lobbying organizations in veterinary medicine. But I say that there are vets working hard towards this goal, and the obstacles they face are significant and not easily overcome.

    One of the most important things people like you can do, in addition to contributing financially to groups like the Morris Animal Foundation, is to tell your vets that you expect evidence-based care and are willing to pay for it, while not being willing to accept less. Economic motivation from clients are much more persuasive for most vets than anything I or others like me can say to them!

  20. Gail McLarnon says:

    Thank you for your in depth response. I actually contribute right now to a JLPP genetic project designed to find the markers for this dreadfull disease for our breed. I donate annually to Walk for the Cure for Cancer in Dogs, having lost two of my own dogs at a very young age to Cancer. I know of the Morris Foundation – and I am quite interested in the 3000 dog GR research trial beginning. I am very interested that it proceeds in a way that yields the best quality research.

    Look the most frequent question I field from novices on the dog boards that I am a member of is 1) what does heat look like, how long does it last? these owners are clueless and they are not necessarily those owners that don’t take their dogs to a vet.

    Then the oopsey matings, again clueless on where to begin and what their options are.
    The AVMA and the CMVA can easily put together a brocheure on this topic. Heck I could do it myself.

    But truly general vets need to deal with this, and educate their clients, and btw themselves – most don’t know anything about intact dogs, unless you are lucky enough to have a vet that is also a breeder. They have no idea of what genetic tests are available out there, or seem to be even interested in the pre-breeding screening tests that are recommended for each breed. And that info is very easily accessibly through CHIC and the National Breed clubs.

    But if each Vet was encouraged to donate $5 for each S+N to a National Donation Health Research Agency – we could self fund the research. You would have owners like myself also donate to something like this.

    At a recent GR fund raiser – a world book Guinness Record was established for the most number of dogs groomed on one day – I think it was 320 or so dogs. Many from rescue etc – the funds raised was over $50,000 and that I think will be going to the GR research study.

    We are having our own fundraiser for our breed this Sunday – and we hope to raise $5000 for the aforementioned study JLPP. We are a whole lot smaller than the GR group 🙂

    Your best friends in evidenced based research are the responsible breeders and owners of purebred dogs.
    Oh my vet knows I am willing to pay for evidence based care. I do all the screenings for my dogs, I do regular full blood work every year, I titer, I utilize chiropractic, and acupuncture and physio when appropriate, I also do Xrays for specific conditions etc. My dogs have weekly or more often as necessary massage. We train regularly in a variety of disciplines. And yes I am not the average dog owner no apologies here for that. And at times the vet and I agree to disagree.

    I look forward to following you more closely to see what is up and coming in the research field

  21. Art Malernee Dvm says:

    The Cochrane Collaboration has actually been lobbied for years to allow veterinarians to form a special interest group, but so far they are not willing. >>>>>
    What do you know about Sweden? I see translated abstracts from that country that makes me believe the veterinarians that publish are more evidence based than the English vets.

Leave a Reply

Your email address will not be published. Required fields are marked *

This blog is kept spam free by WP-SpamFree.