Spay and neuters (full hysterectomies and castrations) are widely held practices in the United States to control pet overpopulation because animals cannot reproduce after this happens. However maybe as a society, we should be looking at what this massive surgery and procedure is doing to a dog's mental and physical state throughout their lifetime. Especially when animals are 'fixed' at a young age without the proper hormones and ability to develop to maturity and go through puberty naturally. 


The United States also has a pet relinquishment problem rather than a pet overpopulation problem. 1.5 million animals are adopted in our country, but half of them are returned each year, the number one reason is behavior issues. 


We encourage dog owners to do their own research and consider ovary sparing spays and vasectomies for their dogs to stop their ability to reproduce but will leave their hormones in tact so their bodies have the necessary hormones for their physical and mental wellbeing. 




The Parsemus Foundation works to create meaningful improvements in human and animal health and welfare by advancing innovative and neglected medical research. 


Innovative Veterinary Care is now  looking at alternatives to the traditional spay and neuter model and will hopefully begin offering these surgeries to their clients, but only if clients ask for this. 


Happy and Healthy Dog is a website dedicated to empowering people with information to make the best decision for their own dogs about a surgery that will affect their dog for the rest of their life, and we encourage you to educate yourself. 



Disclaimer:   This information is taken from Healthy and Happy Dog is intended to provide information helpful to dog guardians, and hopefully veterinarians, as a public service.


Many of the advances in human healthcare and science can be attributed to the fact that we are able to try various medical treatments on our canine best friends before applying them to humans. This is because, from a physiological and biological perspective, humans and canines are very similar. In  fact, we routinely utilize canine models in human medical research (e.g., cardiovascular studies, cancer, heart and lung research, orthopedics, neurology).

Does it make any sense then, that you would take a procedure you know to be extremely harmful to humans (and in some cases illegal) and mandate that it be performed on each and every dog – with almost NO exception and without the benefit of any peer- reviewed research establishing its safety?  And, taking it a quantum leap further, would you then promote this procedure as actually being good for dogs? The quintessential example of this would have to be the spay (ovariohysterectomy) of female dogs and the neuter (castration) of male dogs (please see the section “The Smoking Gun”  for a simplified explanation from an expert). Contrast these overly invasive and often unsafe sterilization procedures with those we safely perform on humans, i.e., tubal ligations on females and vasectomies on males. This begs the question, why can’t vasectomies and tubal ligations be performed on our canine best friends? The short answer is, “They can!”


According to a 2007 systematic review 83 of more than 50 peer reviewed studies regarding the effects of spay/neuter:

“One thing is clear – much of the spay/neuter information that is available to the public is unbalanced and contains claims that are exaggerated or unsupported by evidence. Rather than helping to educate pet owners, much of it has contributed to common misunderstandings about the health risks and benefits associated of spay/neuter in dogs.”

Spay and neuter are also promoted as providing a solution to canine behavioral problems (e.g., aggression, fear and anxiety, excitability) in female and male dogs. However, as observed by Dr. Stanley Coren in Psychology Today, the latest peer-reviewed studies show that contrary to conventional wisdom, spaying/neutering was associated with significantly worse behavior.  Please see sections Behavioral Effects of Spay  and Behavioral Effects of Neuter  for a full discussion of the current studies regarding spay/neuter and canine behavior.

Another oft-repeated aspect of spay/neuter that we must challenge is the assertion that spay/neuter lengthens the lives of our dogs. On our Lifespan page, we discredit a recent study supporting spay/neuter as a procedure which will enhance the lifespan of the family dog. Further, we are able to introduce studies which demonstrate the hormonal imbalance brought on by spay/neuter negatively affects the dog’s ability to respond to stress. This inability to respond to stress creates changes in the dog consistent with accelerated aging and consequently shortens the lifespan of spayed/neutered canines.

With respect to spay (ovariohysterectomy) of female dogs, both the uterus and ovaries are removed to achieve sterilization, with no consideration for hormone replacement. The spay surgery itself is a complex, highly invasive procedure which can lead to serious complications such as stump pyometra, ovarian remnant syndrome, and uterine stump granuloma (see our “Complications of Spay” section for more detail). Add to this the lifelong effects of hormonal disruption, and it becomes clear spay is not a decision to be taken lightly or a procedure that should be “standard operating procedure”. We will utilize current studies/data throughout this website to illustrate spay’s negative medical and behavioral ramifications for healthy female dogs. In healthy human females, if sterilization is desired, we perform tubal ligation. This is much less invasive without the potential complications of spay. Because tubal ligation leaves the ovaries and uterus intact, hormone balance is preserved. Hysterectomy or ovariohysterectomy would only be performed on humans when there is a medical necessity to remove the uterus/ovaries due to disease. In that circumstance, hormone replacement therapy is typically a part of the post-surgical protocol.

With respect to neuter (castration), there is long term evidence regarding the medical ramifications for healthy young human males in previous societies dating back several centuries. The historical information is consistent with data/conclusions from current studies of castration. Due to the long-term medical consequences, we now opt for vasectomy in human males, so as to preserve the testes and the hormones they produce. Surgical castration of human males remains highly controversial, if not illegal, even when performed on convicted sexual predators. A review 81 of the literature on the subject of castration with respect to its medical consequences in previous societies concludes:“Hopefully, it will never again be possible to repeat the studies reviewed in this paper, as in more recent times we have used different means of expressing man’s inhumanity to man”.  The ACLU argues surgical or chemical castration 82 of humans is considered “cruel and unusual punishment”. Why would we inflict this upon our innocent dogs without a second thought?

Why is it “cruel and unusual punishment” to spay/neuter our beloved canine pals? Neuter (castration) removes the testes in the male dog and spay (ovariohysterectomy) removes the ovaries and uterus in the female dog. The testes and ovaries are glands responsible for the production of sex hormones in humans and dogs. They are a part of a group of glands known collectively as the endocrine system. Removal of the ovaries and testes disrupts the production of sex hormones, which, by definition, makes spay/neuter an endocrine disruptor (ED). A disruption in the hormones produced by one gland, or set of glands, can cause other glands to malfunction, resulting in a disruption of the endocrine system as a whole. All this chaos causes unpleasant symptoms, at the very least. Under stress, these endocrine disruptions caused by spay or neuter can lead to a weakened immune system, altered metabolism, chronic disorders/disease, and behavior problems. The present day study of endocrine disruption of this magnitude in humans is limited by ethical considerations. Castrating healthy young human males or removing the ovaries and uterus of healthy young human females with no intent to provide hormonal replacement would never be permitted.

There are a group of chemicals, both natural and man-made, that exist in our environment and are classified as endocrine disruptors (EDs). These EDs have been studied in humans and wildlife. Most of these EDs do their damage by mimicking or blocking male and female sex hormones. For example, in males, EDs effectively “chemically castrate“ 70 (i.e., neuter) their victims. The names of some of these EDs might be familiar to you and include DDT, dioxin, BPA, PFOA, atrazine (herbicide), PCBs, and arsenic. The effects on humans of exposure to these EDs is quite similar to the effects of spay/neuter on our young dogs. We will explore this in depth in the Diseases section of this website, where we will refer you to resources from the Hormone Health Network. The Hormone Health Network is the public education affiliate of the 100 year old Endocrine Society – the largest global membership organization representing professionals (medical doctors, scientists, researchers, and educators) from the field of endocrinology.

At a recent European Union (EU) conference on endocrine disruptors,65 R. Thomas Zoeller, PhD, an invited spokesperson for the Endocrine Society, stated "Spay/neuter is the ultimate ED, and it is never a responsible option for a young, healthy dog." Yes, we said NEVER. The conclusions of Dr. Zoeller (just above), with respect to endocrine disruptors are remarkably similar to the conclusions in a 2013 UC Davis study of the effects of spay/neuter:  once a dog has been spayed or neutered, their endocrine system has been forever altered. There is no going back to optimal health, despite best efforts. In fact, we will illustrate on our Diseases Overview and the Stress Response System pages of this website how spay/neuter permanently damages your dog’s ability to respond to physical and/or psychological stress; leaving your dog increasingly susceptible to cancer, metabolic disease including diabetes, immune-related disease, infection and anxiety. The damage of spay/neuter to the endocrine system of your dog is permanent, and no dog is immune.

We will summarize the multitude of studies revealing the consequences of spay/neuter in the Spay and Neuter sections of this website (note: there are over 170 peer reviewed studies referenced in our Bibliography). We will document the developmental damage of early spay/neuter in the Orthopedic section and the emerging chronic diseases related to spay/neuter in the Hormones and the Endocrine System section of this website. The Research section explains why it is acceptable to apply the research and studies pertaining to endocrine diseases in humans as a basis for understanding the emerging disease entities in dogs. In our History section, we will discuss at great length how our dog Billy’s health problems led us to our conclusions.

In short, spay/neuter significantly increases the risk of an otherwise young, healthy dog developing:

  1. Orthopedic problems

    • hip dysplasia

    • elbow dysplasia

    • CCL ligament tear in their knees (requires TPLO surgery)

  2. Cancer

    • osteosarcoma

    • hemangiosarcoma

    • Lymphosarcoma

    • mast cell tumor

  3. Diseases of the endocrine (hormone) systems

    • hypothyroidism

    • Cushings and Atypical Cushings

    • Type 2 diabetes

    • Hyperestrinism and Alopecia (hair loss)

    • Allergies (atopic dermatitis)

    • Obesity

  4. Behavior problems

    • aggression towards people and other dogs

    • fear and anxiety

    • reactivity to touch or handling

Spay/neuter, the ultimate endocrine disruptor, is key to the increase of all of the seemingly unrelated detrimental conditions our dogs suffer from as documented throughout this site. We recognize spay/neuter is a means to an admirable goal. However, is it ethical to compromise the right to a healthy and happy life for the individual dog for the perceived “greater good” of controlling dog overpopulation?  A 2012 Texas A&M research paper 99  titled, “Inconvenient Desires: Should We Routinely Neuter Companion Animals?”, explores this very question. Summarizing their conclusions: Routine neutering of companion animals raises significant ethical questions and from some ethical perspectives, looks highly problematic. In the case of male dogs and the long-term health risks involved, routine neutering is not morally justified.

We don’t believe any dog should be condemned to a life of pain and illness when viable alternatives which protect your dog’s hormones exist. We would strongly recommend the time and human tested procedures of tubal ligation and vasectomy as safe and ethical alternatives to conventional spay/neuter for our dogs. This solution also prevents pet overpopulation.  According to a 2001 published UC Davis Behavior Service study 55: “There may be a need to evaluate possible methods for counteracting the effects of loss of sex hormones in gonadectomized [i.e., having had ovaries or testes surgically removed] dogs.” (Dr. Benjamin Hart;  School of  Veterinary Medicine, UC Davis; J Am Vet Med Assoc 2001; 219:51–56)

Further, in 2013 60 and 2014,61 UC Davis published studies linking spay/neuter to three significant orthopedic problems and four aggressive cancers. One might reasonably question why UC Davis has not moved to revamp their curriculum to reflect their own studies. Certainly, if that were the case, they would be promoting tubal ligations and vasectomies as a superior alternative. Oddly enough, we located an interview with the researchers responsible for the 2013 UC Davis study (see our “Smoking Gun” page) wherein it is acknowledged tubal ligation and vasectomy would control canine overpopulation without the increased prevalence of deadly cancers and orthopedic deformities. There is no answer provided by these researchers as to why they are not promoting or teaching tubal ligation or vasectomy.


It appears that change will only occur as a response to pressure from pet guardians. In fact, the authors of at least one study acknowledge the adverse effects of spay/neuter and encourage veterinarians to discuss the harmful effects of spay/neuter with their canine guardians.109 Therefore, at this time it would seem appropriate to introduce/reacquaint your veterinarian to a concept known in human medicine as “shared decision making63 (SDM).  Sharing decisions, as opposed to clinicians making decisions on behalf of patients, is gaining increasing prominence in health care policy. 

If a significant number of pet guardians demand tubal ligation and vasectomy as a method of population control, the veterinary surgeons will respond accordingly and educate themselves on the intricacies of these surgical procedures. We are told by experts in the field that these procedures are simpler (from a technical perspective), have fewer complications and should ultimately be less costly. This should appeal to shelter managers and other custodians of the bottom line as well. If you have difficulty locating a veterinarian in your area who is capable and willing to perform hormone sparing sterilization alternatives to traditional spay/neuter (e.g., vasectomy, tubal ligation, ovary sparing spay), we recommend that you refer to our Frequently Asked Questions (FAQ) or our Facebook page.

Should the veterinary community get on board with our recommendations with respect to hormone sparing sterilization alternatives to traditional spay/neuter, any laws requiring spay/neuter can easily be amended to require “sterilization”. This would not preclude spay or neuter if that was desired, but also allow tubal ligation and vasectomy as legally valid options. We would also be positioned to take advantage of new procedures to prevent reproduction that technology may bring us in the future. Please visit our Legal section for information regarding each state’s law and a detailed discussion on how to change your state law if necessary.

We are making progress! If you visit our Legal section you will see that in 2016, both the American Veterinary Medical Association (AVMA) and the American Society for the Prevention of Cruelty to Animals  (ASPCA) only recognized/recommended spay/neuter as legitimate methods of preventing pet overpopulation. Today, however, the AVMA recognizes other hormone-sparing procedures specifically, and the ASPCA recommends “sterilization” which would also allow for hormone-sparing procedures as we are advocating.

If your current dog has already been spayed/neutered, the damage has most likely already been done to a large extent. We will do our best to advise you of offsetting measures that were somewhat successful for our dog and/or that we discovered in our research. We ask that you please work with us to change the status quo for all pets – present and future.