New protocols to enhance your practice and benefit your clients and community
W. Marvin Mackie, D.V.M.
Inter Zoo Publishing Co.
Osaka, Japan
November 2005

I am honored by the request to present the concept of juvenile sterilization to my Japanese colleagues.  Over the past seven years, I have hosted several Japanese veterinary students in my clinics and in September 2004,  I was invited to Japan to speak at  the Japanese Board of Veterinary Practitioners annual meeting in Tokyo.   The purpose of my presentation was to acquaint Japanese veterinarians with the concept of juvenile sterilization as it is performed in the USA.  Although pet overpopulation concerns are not reported to be as critical in Japan as they are in the United States, Japanese humane groups are beginning to understand the impact of over birthing and are looking toward the prevention of a crisis.  It is my understanding that sterilization is not usually encouraged by the family veterinarian but is willingly performed at the client’s request.  With this in mind, I would like to present a concept that will enhance your veterinary practice, increase your skills and benefit your clients and community.  When humane groups and/or shelter officials come to you requesting help with pet overpopulation, you will be well qualified to respond with confidence.

In the early 1970s, those in charge of animal impoundment in the United States began informing the nation’s humane community and veterinarians of the unacceptable killing of a estimated 15 to 18 million companion cats and dogs annually.  The obvious problem was animal birthing beyond the capacity to place them in loving homes.  The supply of pets far outnumbered the demand. 

When these disturbing numbers were brought to the forefront, the humane community and concerned citizens began asking veterinarians to help them by educating their clients that sterilization of companion animals is an important part of responsible pet ownership.   In addition, many  animal adoption groups and shelters realized that instituting a policy of sterilizing their animals before releasing them for adoption would make a vital contribution to the solution of pet overpopulation.  As a result of the aggressive campaign for companion animal sterilization, euthanasia dropped dramatically over the next 20 years and by the early 1990s the figure reached 7 to 8 million per year.  Although this was progress, it was not good enough for those who were committed to eliminating pet overpopulation and working toward becoming a no-kill nation.

While doing relief work in a spay/neuter clinic in the mid-1970’s, I began to consider the value of high volume spay/neuter surgery.  This was an idea where even one dedicated veterinarian could make an impact on the local pet overpopulation problem.  It was at that time that I began my life’s work as a spay/neuter surgeon.  I opened my first of five spay/neuter clinic in the Los Angeles area in 1976.  Through my long involvement in the control of pet overpopulation, I have come to realize that over-birthing is a worldwide problem.  My colleagues and I receive pleas for ideas and help from foreign countries, districts, towns and even remote islands that are overburdened with surplus dogs and cats.  I encourage all who ask to seek help from their local veterinarians to educate their clients and the community that sterilization is the most important and most humane method to permanently correct pet overpopulation.  They tell me that unfortunately their local veterinarians are of little or no help.  Since only we veterinarians can perform an ovariohysterectomy, our communities are dependant on our involvement.

For years, veterinary schools in the United States taught that the preferred age for sterilization was 6 to 10 months of age.  This recommendation cannot be tied to any particular study but it is believed to be a result of a consensus of the veterinary practitioners performing the surgery during the mid-1940s through 1950.  At that time, the drugs, anesthesia and equipment were geared for the larger and more mature patient.   Six to 10 months seemed an acceptable size and age irrespective of the female’s first estrous or the male’s development. Unfortunately, by waiting 10 months or more, females were often past their first estrous and many accidental pregnancies had already occurred.  Our age protocol was defeating our goal of preventing unintended pregnancies.  With the growing demand for sterilization to curb the pet overpopulation problem, our profession was challenged to question the age at which sterilization was recommended.  If we wanted to be a major contributor in the effort to reduce over birthing, we needed to update our thinking. 

In 1987 a remarkable colleague, Leo L. Lieberman, D.V.M., authored an illuminating study entitled “A Case for Neutering Pups and Kittens at Two Months of Age”,  Journal of the American Veterinary Medical Association, Vol. 191:518-521, 1987.  Dr. Lieberman studied three shelters performing sterilizations on very young adoptees and found that surgery performed on dogs and cats as young as 8-weeks was safe and successful.  By pursuing his convictions on juvenile sterilization, he took the giant step that challenged our out-dated belief that we needed to wait 6 to 10 months for the surgery.  His study of those shelters and his advanced thinking led him to the conclusion that juvenile sterilization should be the standard procedure. 

Those who were closest to the over birthing problem rejoiced at the news;  however, most of the veterinary profession were in opposition, due mainly to an unfortunate human flaw – resistance to change.  In spite of the fact that some early 1900s journals referred to non-suture spays of two-month old pets and the fact that some commercial puppy farms were sterilizing three month old females just before mail order delivery, this change flew in the face of our teaching and long established beliefs.   It was viewed as a radical and dangerous approach to sterilization.

There was a large and vocal group of veterinarians who predicted dire consequences.  Generally, their concerns fell into two categories:  1) the health and development of the animal and 2) the anesthesia and surgical safety.  Immediately, studies were undertaken to prove or disprove the validity of those concerns.

A pivotal study looking into the health and developmental concerns of juvenile sterilization was reported in the Journal of American Veterinary Medical Assn., April 1991.  In the study, thirty-two male and female pups from five litters were divided into three groups.  Group 1 was neutered at 7 weeks, group 2 was neutered at 7 months, and Group 3 remained unaltered as the control group.  Six different parameters were regularly checked and evaluated until the pups reached 15 months of age.  The eleven-page report at the conclusion of the study included discussions and the results.  The core conclusions were  that the measured differences between those neutered at 7 weeks of age and those neutered at 7 months of age were statistically insignificant.  There were some differences between neutered groups 1 and 2 and the unaltered group 3.  The profession has long since determined that these were  normal and acceptable differences. 

Next was a similar study using kittens instead of pups.  The study is summarized with this statement: “It was concluded that neutering at 7 weeks and 7 months of age had similar effects on skeletal, physical and behavioral development in the domestic cat.”  In a personal conversation with the theriogenologist who was the senior advisor of the project, I was told that prior to conducting the study, she fully expected to find problems that would indicate the inadvisability of sterilization upon the very young cats.  After the study however, she said that she could support a recommendation to move the elective surgery to the much younger age. 

In an article in DVM Magazine, Dr. Johnny Hoskins, DVM, PhD, ACVIM, author of Veterinary Pediatrics, referred to a legitimate list of concerns from fellow DVMs regarding juvenile sterilization.  He offered that there is “…no evidence in the literature to support claims that early age (juvenile) sterilization increases risk.”  Additionally, he stated, “…the advantages far out-weight the risks.”  The findings of these studies gave reassurance to those of us doing juvenile work. 

With regard to the safety issues, we found that in contrast to the expected anesthetic intolerance, the youthful patient is quite resilient and does very well with our modern anesthetic agents.  Progress in anesthesia over the last 20 years has blessed our profession with several incredible injectable compounds and two truly fine inhalant compounds.  The injectables (Ketaset, Telazol, Rompum, Acepromazine, and Valium) can even be mixed for further enhancement of the perfect anesthetic plane for surgery.  In lesser doses (considered pre-op levels), the injectables can be topped up with low levels of inhalants such as Halothane or Isoflurine.  When delivery dosage is accurately proportioned to the smaller size, it is well tolerated by the juvenile.

In 1994, a small informal publication listed eleven different anesthesia protocols being used by veterinarians; each with its own devotees.  It was clear to me that whatever protocol is being used for a mildly invasive, short, well-animal surgery could and should be adapted for the juvenile sterilization patient.   It is more important that the veterinarian be comfortable with a known protocol of anesthesia and patient responses than to adapt to a colleague’s protocol that is unfamiliar.

The amazing tolerance of the pre-pubescent to anesthesia and the surgical procedure itself is best illustrated in a study by Texas A& M wherein senior veterinary students, in a teaching environment, performed spay/neuters on 1,988 subjects ranging in age from eight weeks to over five months.  The study was designed to report any short-term complications.  The incidence of complications was the lowest for the less than 12 weeks of age group.


This observation speaks well for itself.   However, what really stands out is the length of time these teaching patients were under anesthesia during prep and surgery.  Rounding off for brevity, females were “in surgery” for 60 minutes +/- 23 minutes, males for 21 minutes +/- 17 minutes.  This is an astonishingly long period of time!   It certainly points out the juveniles’ resilience and ability to tolerate the procedure.  Since an expected surgical time is 10 to 20 minutes, this study should be extremely valuable as a confidence builder for the uneasy practitioner.

To all practitioners, the thought of moving from and eight-month old patient to an twelve-week old patient can be daunting.  We have the feeling that something so small and immature must also be delicate and therefore tolerate a minimal latitude for error.  Quite the opposite; these furry little creatures are marvelously resilient and quickly recover from this relatively short procedure.  For the age group of four months and older for pups and three months and older for kittens, there are no special needs or concerns. You may use your established anesthetic protocol and general elective surgery instructions to the client. 

I recommend trying a female kitten first.  A three-month-old female kitten’s uterine horn is easily captured by the spay hook.  I hear the anguish from colleagues lamenting over fat and/or the estrous engorged uterus of a one-year-old female cat.   Waiting seems ill-considered when a 12-week surgery is within our recommendation.

I’d ask you to visualize a four-month-old Akita female weighing approximately 15 kilograms.  Now visualize her at 14 to 16 months, full bodied and active and weighing 40 kilograms.  The pet owner doesn’t want her to go through another estrous cycle.  Which animal would you rather spay today? 



When performing a spay on the prepubescent juvenile pup or kitten,  the entry is a small 1 ½ (kitten) to 2 cm (pup) incision exactly mid-way between the umbilicus and anterior brim of the pubis.  You will find without exception:

  1. Less bleeding
  2. Excellent visualization
  3. Elastic tissue for easy ligature placement
  4. Everything in miniature and prepubescent; therefore, less stitching and less time required.
  5. Fewer drugs required
  6. Quicker recovery and healing with less patient discomfort
  7. Near zero complications
  8. Delighted clients

This list is a powerfully positive incentive to consider adding juvenile spay/neuter to your list of services.

I encourage you to add this protocol to your list of specialties and remind you that a surgeon becomes skilled and competent with practice; there is no substitute for experience.  A comfort level with anesthesia comes with multiple successes in the surgical room.  Expertise in the use of surgical instruments and the suture material comes gradually as the surgeon’s eye/hand/neuromuscular pathways develop confident moves.

Consider also the health benefits to the pet.  Female dogs have a near-zero chance of developing mammary tumors if spayed before the first estrous.  After the first or second estrous, one-third or more female dogs risk the development of tumors.  Female cats are induced ovulators and can suffer in some state of continued estrous for months if not serviced by a male.  Intact male cats are noted for their fighting, abscessed wounds and the spread of disease due to their response to the hormonal surge.

And the benefits to your clients must be emphasized.  When sterilization is performed on their pet at four months of age, there will be no surprise litters.  They will not be subject to their female pet’s hormonal driven frenzy and the required confinement if a litter is unwanted.  Nor will they have to endure their male pet’s inclination to roam and/or spray due to a neighbor’s in-estrous female.  Their pet will tend to be a calmer and less distracted companion.

The acceptance of juvenile sterilization in the United States has been an uphill climb but it has been a rewarding one.  Throughout the nation, veterinarians are recognizing the importance of a diligent sterilization program.  Many DVMs in the United States are now willingly performing sterilizations on patients four months of age.  It has become clear that such a program benefits the pet, the pet owner and the community.

But how will a program such as this benefit you?  I have suggested the need to broaden the parameters and general recommendations of surgical sterilization for the benefit of the Japanese society in general and specifically for the benefit of the pet owner.  Now I would like to discuss the personal and business advantages to the veterinarian.

As it appears to me, surgical sterilization is overlooked as a normal part of the well-animal service in Japan.  Given the patient and client advantages of the procedure, there is a real potential to increase practice revenues with client education and recommendation.  Pet wellness programs are a delightful part of our veterinary practice.  Most of the time, we are attending an enthusiastic client with a new puppy or kitten that is generally healthy.  Along with vaccinations, parasite control, diet and behavioral care, veterinarians should confidently recommend and promote sterilization to coincide with the last vaccination of the series.  Pet owners do not resist this idea from their trusted professional.  Typically in the United States, the last vaccination and the spay/neuter would be scheduled at three months for kittens and four months for pups.   This timing is convenient for the pet owner as it eliminates the need for an additional visit and it prevents the chaos of raging hormones and the accidental litters which occur all to frequently due to procrastination in scheduling a spay.  Many veterinarians offer a moderately priced pre-paid well-animal package of services which includes sterilization.  The savings motivate clients to purchase the package rather than purchase each of the services individually at a higher price.  
And once paid, they are motivated to take advantage of the complete package, including the sterilization of their pet.  

Juvenile spay/neuter can be both financially and professionally rewarding in any veterinary practice.  It can add revenue, improve surgical skills and develop a confident, capable surgical team.  Should you decide not to aggressively promote spay/neuter and include juvenile sterilization as a part of your practice, please do not discredit any colleagues who chose to move forward with the procedure.  Eighteen years have passed since Dr. Lieberman published his article in support of juvenile sterilization and all of the ensuing studies have shown favorable results from the practice.  The developmental differences that were noted were not problematic.  And for years, reluctant colleagues countered the findings with “we still don’t know about the long term effects”, to date, there have been no meaningful long-term health issues reported.  Two retrospective studies looked at the long term risks and benefits of early age gonadectomies in dogs and cats.  The only caution found was that female pup spays should be delayed until three months of age.  Beyond this one suggestion, the studies were able to support sterilizations for the very young as well. 

You will note that throughout my discussion of juvenal gonadectomy, I recommend using the guidelines of 3 to 4 months of age.   I used this age group primarily due to the ease of surgery of these patients and the convenience of the timing for a general practice plan.  In my practice, I eventually began to perform sterilizations on 7 to 8 week-old pets and realized equal success.  There are some additional considerations for the 2-month old patient, as you would expect with any surgery on so young an animal.  As you become comfortable with juvenile sterilizations, you may find reason to advance to the younger age.    You can be assured that the precedent for this procedure has long been established in the United States. 

Juvenile spay/neuter is a progressive and rewarding step forward in the services we can offer our clients.  I hope many of the Japanese hospitals will include this in their menu of services.