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What is The Difference Between
The OE And The OHE Spay Procedure In Dogs And Cats?

Most veterinarians in the USA are reluctant to perform an OE (ovariectomy)
spay procedure on dogs and cats because they have been doing primarily the OHE (ovariohysterectomy) procedure for years.  Nevertheless, ovariectomy has been the preferred spay procedure in Europe for many decades.  Thorough and extensive valid research has been done in Europe regarding the safety, efficiency, and effectiveness of the OE procedure.

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Call your local veterinarian if your pet is sick or if you need advice about a specific pet.

Someone told me they heard of a vet doing a different spay procedure than most vets.  The vet in question was only removing dog and cat ovaries during the spay surgery and leaving the uterus.  I was surprised!        What's the difference between an ovary removal only and a spay by removal of ovaries and uterus?



FACT:  The study of endocrinology focuses on the glands in the body that secrete chemicals called hormones and the hormone target tissues.  Hormones have a profound effect on their target tissues.  Increased hormone secretion from, for example, a hormone secreting tumor, will over-stimulate the target tissue.  Less hormone secreted, as after removal of testicles or ovaries, results in sex hormone absence resulting in atrophy of the sex hormone target tissues such as the prostate and uterus. 


A dog ovary obtained during an OHE... ovariohysterectomy surgery

A dog ovary obtained during an OHE... ovariohysterectomy surgery


Spay incisions can vary according to each unique patient

Answer:  dogs and cats... spay... difference between OE and OHE
     This question pops up more frequently lately so we will explain the difference between a spay surgery by OE versus an OHE.
  First... An OE spay is an ovariectomy, which means removal of the ovaries only.  An OHE is a spay procedure where both ovaries and both uterine horns and a small portion of the uterine body is removed.

  Second... OE spays have been favored in Europe for many years; OHE spays have been preferred in the USA for many years.

  Third... both methods will permanently terminate heat cycles in the female cat or dog as well as remove the female sex hormones' influence on the target tissues.

  Fourth... in young dogs and cats with normal uterine health, either before or after a heat cycle, removal of the ovaries causes any remaining uterine tissue to atrophy (shrink or decrease in size).

  Fifth... in older dogs or cats, patients that have had several litters, or patients with any suspected abnormality in the uterus, an OHE may be the preferred spay procedure.  The decision is up to the attending doctor.

  Sixth...  A number of veterinary associations in the USA such as some state veterinary associations and the AVMA (American Veterinary Medical Association) state that the decision to do either procedure is up to the attending doctor.  These associations take no position, pro or con, regarding which spay procedure the doctor should use.

Many reviews analyzing the safety and time savings of doing an OE versus an OHE reveal a net benefit to the patient for having just the ovaries removed and leaving the uterus in place.  In fact, there is no evidence anywhere that indicates there is a greater risk of eventual uterine pathology such as pyometra, bacterial endometritis, cystic endometritis in dogs and cats that had OEs done compared to dogs and cats having an OHE done.

In spite of a 2010 article in the AVMA Journal (JAVMA) about a small study that found no difference between the two procedures, there was a surprising and unintuitive comment in that study's Summary.  It stated the surgical time needed to do either methods was identical... even though the study showed the OHE procedure required a longer incision and required more sutures to close the patient.  See the image below on the right.

I hope this answers your question!  Expect a staunch difference of opinion among veterinarians regarding which method of spaying healthy dogs and cats is best.  Perhaps we could simply assume the best procedure is the one your doctor feels most confident doing, whether or not it is an OE or OHE.

Having done spays for over forty years I opt for the OE procedure when appropriate for several safety and efficiency reasons.  Just to be clear... I am not advocating the OE procedure for every patient.

T. J. Dunn, DVM
Research Articles are at the bottom of this page.

Doctor's Notes
     In an article in Veterinary Practice News by Dr. Phil Zeitman, a Board Certified Specialist in Veterinary Surgery, he states, " If the uterus is healthy in a healthy, nongravid female that is spayed before her first heat, then performing an ovariectomy should be acceptable. If there is any doubt that the uterus may not be healthy, then an ovariohysterectomy is medically indicated."

Dr. Zeitman states, "
Why couldn’t more than one standard of care exist for a medical procedure as long as it is scientifically and ethically acceptable?"

"Each practitioner should have the prerogative of deciding which procedure is better for each patient. This is no different than deciding which vaccination protocol makes the most sense, or which procedure is better to stabilize a torn ACL, or which suture pattern is ideal for a cystotomy, or which gastropexy technique is stronger for bloat, or which drug cocktail is safer for anesthesia.  It’s a judgment call."

View of an ov
(spay or OHE) in a cat

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Click on an image to view a larger version in a new window
Cat spay by OE... ovariectomy surgery Cat spay by OE... ovariectomy... Dog ovary,spay,OHE,OE,fatty tissue,surgery,veterinary OE spay incision length...ovariectomy
A cat spay by OE... ovariectomy...
The ovary is exposed and suture material is ready to tie off vessels
A cat spay by OE... ovariectomy...
The ovary is exposed and suture material is ready to tie off vessels
An ovary of a dog with surrounding tissues.  Note all the fatty tissue which makes the spay surgery more difficult A typical short OE spay incision four days post op.  There are no external sutures to attract the pup's attention!

     I'm a retired veterinarian and never have done an OE for fear that leaving uterine horns in the patient would increase the risk of uterine pathology some time in the future.

     Isn't it rather intuitive that if you leave a hollow organ such as uterine horns and uterine body in the patient there has to be increased risk of such problems as pyometra?

Cystic endometritis in a dog durin a spay surgery

Cystic endometritis in a dog... one uterine horn has been incised to view the extent of the pathologic changes occurring in the uterus due to hormone stimulation

Answer:  dogs... cats... OE vs OHE... uterine pathology
     Your fears were the same as mine, Doctor, until I acknowledged that fact that uterine pathology, organ growth, tissue hypertrophy and other factors result from the impact the gonadotrophic hormones have on the target tissue... in this case the uterus.  Hormones from the pituitary gland stimulate ovarian hormone production.  These female hormones determine uterine physiology and anatomy.  Remove the ovaries and essentially no female hormones are secreted to affect the uterine target tissues.
     It's analogous to why we recommend neutering male dogs... the removal of the source of male hormones from the testicles take away the fuel for growth and function of the prostate gland.  Prostate problems in older male dogs that have not been neutered often get relief through neutering by permitting the prostate to atrophy over time because the prostate growth stimulus factors from male hormones are no longer present.
     Remove the ovaries from a dog or cat and the female hormones targeting the uterus no longer send commands to the uterus so it shrinks and degenerates. The uterus is a hormone sensitive target tissue; remove the hormone and the target tissue undergoes disuse atrophy.
I did an OE on my 4 month old rescued Chihuahua and about a year later needed to do an abdominal exploratory surgery for an intestinal foreign body obstruction.  (She decided to eat some kleenex which refused to move!)  During the surgery I looked diligently for the uterine horns and body and saw what I thought used to be those tissues but honestly couldn't define their presence.

Links to Articles are at the bottom of this page.

Images of spay surgery

Pyometra in a cat due to cystic ovaries

Pyometra in a cat due to cystic ovaries

Pyometra in a cat due to cystic ovaries
Cat ovary and cyst

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The December 15, 2011 issue of the Journal of the American Veterinary Medical Association (JAVMA) published an article by Drs. DeTora and McCarthy, Dept. of Clinical Sciences, Cummings School of Veterinary Medicine, Tufts University.  The article evaluates the OHE and OE procedures as done on young, healthy female dogs and cats.  Their view is that there is no scientific basis upon which to state or teach the OHE as a preferable technique over the OE procedure in young, healthy female dogs and cats. In addition their view is that there are no recognized disadvantages to performing the OE procedure and there are several potential  advantages to doing the OE procedure rather than the OHE.



Prepared by T J Dunn, DVM
Naples, FL
Rhinelander, WI


Dr. Dunn,
The WMVA does not have a position on this.  However, in talking with some of the WVMA Leadership it seems like either would be acceptable.
Kim Brown Pokorny
WVMA Executive Director


(To quickly scan visually for primary information read the highlighted blue text.)

Definitions for this review:

OHE = Ovariohysterectomy:  The patient’s ovaries and the uterus above the cervix is removed.

OE or OVE = Ovariectomy:  The patient’s ovaries are removed and the uterus is left intact.

Appropriate patient for OE procedure:  A patient that is healthy and has not had a litter, nor has a history of uterine pathology, nor displays any evidence of uterine pathology to the surgeon at the time of the spay surgery.

Best procedure:  The one procedure of many that provides a solution for doing the surgery and that has the least potential to harm to the patient.  (This definition is arrived at objectively.  It is  based upon knowledge of anatomy, physiology, aesthetology, and other scientific data.) 

Most efficient:  The procedure that takes the least time, effort, cost, and maintenance.  (This definition is subjective in nature.  The most efficient procedure is determined by considering the surgeon’s skill, staff’s skill and compatibility, pre and post op practice protocols, anesthetic selection and other individual habits and priorities.) 

Goal:  The goal of this review is to present just a few of the current references relating to the two commonly used methods of surgical sterilization… ovariohysterectomy and ovariectomy.  The published literature will assist anyone wishing to understand, compare, and contrast the safety and efficiency of two different procedures when used on appropriate patients. Objective scientific data as well as subjective preferences of surgeons and staff should lead the inquiring mind to a conclusion regarding the best spay procedure to use on appropriate patients.


Many reasons exist for performing ovariectomies instead of ovariohysterectomies in healthy bitches. Compared with ovariectomy, ovariohysterectomy in dogs is technically more complicated and time-consuming and is likely associated with greater morbidity (larger incision, more intraoperative trauma, increased discomfort).1 No significant differences between the two procedures have been observed for the incidence of long-term urogenital problems, including endometritis, pyometra, and urinary incontinence.1 In addition, there is no benefit and, thus, no indication for removing the uterus during routine neutering in healthy bitches.1


Sixth Edition  Ettinger and Feldman;  Vol. 2

Although OHE is the most common technique used for permanent female sterilization in the United States, it has been shown that the long term side effects associated with only performing ovariectomy are no different than when OHE is performed.  The advantages of performing OE include shorter surgery time, a smaller incision, and less abdominal trauma.  Perhaps North American veterinarians should contemplate the advantages of OE over OHE.

International Congress of the Italian Association of Companion Animal Veterinarians

May 30 – June 1 2008  Rimini, Italy

Ovariectomy versus ovariohysterectomy.  Is the eternal argument ended?

Jolle Kirpensteijn  DVM, PhD, Dipl ECVS, Utrecht, Olanda

Gonadectomy can be performed by

ovariectomy (OVE) or ovariohysterectomy (OVH), the latter

being the preferred approach in the USA. This preference is

most likely based on the presumption that future uterine

pathology is prevented by removing the uterus. In the

Netherlands and some other European countries, OVE is

routinely performed and has replaced OVH as the standard

approach for gonadectomy; the uterus is only removed when

uterine pathology is present

Endometritis and pyometra

Epidemiologic data for ~200,000 dogs covered by insurance

in Sweden revealed that ~ 1,800 non-spayed bitches

were treated for pyometra in 1996. The risk of an intact bitch

developing pyometra before 10 years of age was 23 - 24%.

Other studies, albeit on a smaller scale, had similar findings.

Fukuda reported a 15.2% chance for the development of

pyometra in 15.2% chance female dogs > 4 years old (n =

165) and Von Berky reported a 14.9% chance for uterine disease

(n =175).


Thus, it is important to determine if the uterus in ovariectomized

dogs is predisposed to develop endometritis and

pyometra. Pyometra has been defined as a hormonally mediated

diestral disorder resulting from bacterial interaction

with an abnormal uterine endometrial that has undergone

pathologic changes assumed to be caused by an exaggerated

response to progesterone stimulation. Recently, the concept

of considering cystic endometrial hyperplasia (CEH)-

pyometra as a complex has been questioned. It has been suggested

that 2 different disorders; one where CEH-endometritis

appears to have a strong hormonal component and

pyometra might be more influenced by the bacterial component.


Nevertheless, both conditions are exclusively encountered

in the luteal phase of the oestrus cycle. Experimentally

CEH or CEH-endometritis can be induced by administration

of progesterone, even in ovariectomized bitches. Withdrawal

of progesterone treatment causes regression of the

naturally occurring disease. Thus exposure to progestagen

appears to be necessary for the development of CEH-endometritis.


A study by Okkens et al comparing the long-term effects

of OVE versus OVH was conducted at the University of

Utrecht in 1997. Questionnaires were sent to 264 owners of

bitches that had either OVE (n = 126) or OVH (n = 138) performed

for routine neutering 8-11 years earlier. Complete

data were obtained for 69 OVE bitches and 66 OVH bitches.

None of the OVE bitches had signs consistent with having

had endometritis. With the exception of urinary incontinence,

no other problems related to surgical neutering were

identified. These findings agree with those of Janssens who

performed ovariectomy on 72 bitches and after a 6 - 10 year

follow-up, no pyometra was detected. When OVE is correctly

performed (all ovarian tissue removed) and in the absence

of supplementation of exogenous progestagens, endometritis

(CEH or pyometra) cannot occur.

These studies strongly suggest that progesterone is an essential factor in the occurrence of CEH-endometritis-pyometra and that correctly performed, OVH or OVE will prevent development CEH-pyometra in later life. OVE will not increase the chance for development of CEH-pyometra compared with OVH.

Since 1981, after introduction of OVE as the standard

technique for canine neutering at Utrecht University, no

increase in short-term complications has been observed.

With respect to long-term urogenital problems, including

endometritis/pyometra and urinary incontinence, it has been

clearly established that they do not any occur more frequently

with either technique.

The overall chance for development

of uterine tumours is very low (0.003%), and, in our

opinion, does not warrant performing a potentially more

traumatizing surgical procedure, OVH, that might be associated

with more postoperative complications.

Without benefit of more prospective studies comparing

surgical complications between OVE and OVH, most evidence

extracted from the literature leads us to the conclusion

that there is no benefit and thus no indication for removing

the uterus during routine neutering in healthy bitches. Thus

we believe that OVE should be the procedure of choice for

canine gonadectomy.

Reprinted in IVIS with the permission of Close window to return to IVIS

Proceedings of the International SCIVAC Congress 2008

From VETERINARY SURGERY Volume 35, Issue 2

Making a Rational Choice Between Ovariectomy and Ovariohysterectomy in the Dog: A Discussion of the Benefits of Either Technique


  1 From the Department of Clinical Sciences of Companion Animals,
Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands

Correspondence to  Address reprint requests to Bart Van Goethem, DVM, Spoorweglaan 38A, 9140 Temse, Belgium. Copyright Copyright 2006 by The American College of Veterinary Surgeons


Objective—To determine if ovariectomy (OE or OVE) is a safe alternative to ovariohysterectomy (OVH) for canine gonadectomy.

Study Design—Literature review over a 35 year period.

Methods—An on-line bibliographic search in MEDLINE and PubMed was performed in December 2004, covering the period 1969–2004. Relevant studies were compared and evaluated with regard to study design, surgical technique, and both short-term and long-term follow-up.

Conclusions—OVH is technically more complicated, time consuming, and is probably associated with greater morbidity (larger incision, more intraoperative trauma, increased discomfort) compared with OVE. No significant differences between techniques were observed for incidence of long-term urogenital problems, including endometritis/pyometra and urinary incontinence, making OVE the preferred method of gonadectomy in the healthy bitch.

Clinical Relevance—Canine OVE can replace OVH as the procedure of choice for routine neutering of healthy female dogs.



Submitted April 2005; Accepted June 2005

Source: Okkens, AC, Kooistra, HS, Nickel, RF (2003): Comparison of long-term effects of ovariectomy versus ovariohysterectomy in bitches
In: Der Praktische Tierarzt, 2003, Vol 84, Iss 2, pp 98-101

Neutering of bitches is a routine surgery in small animal practice. If ovariectomy or ovariohysterectomy is performed, is a common point of discussion. In this study, 135 dog owners answered questionnaires concerning their bitches neutered years ago with either ovariectomy or ovariohysterectomy.

The present study compares long-term effects of ovariectomy versus ovariohysterectomy in the bitch. Questionnaires were sent to 264 owners of bitches, in which ovariectomy or ovariohysterctomy had been performed as a routine neutering procedure 8-11 years earlier. Complete data were available for 69 bitches of the ovariectomy group and for 66 bitches from the ovariohysterectomy group. There were no indications that endometritis had developed in bitches of the ovariectomy group. None of the bitches was sexually attractive to male dogs after neutering. The occurrence of a clear to white vaginal discharge was reported in two bitches of each group, but none of these four bitches appeared to be ill during the period when the discharge was present. Furthermore, with the exception of urinary incontinence, no problems were reported that could be related to the surgical neutering. Six of the ovariecto- mixed bitches and nine of the ovariohysterctomized bitches eventually developed urinary incontinence. Of these 15 bitches (11 %), 12 weighed more than 20 kg. Bouvier des Flandres bitches were at a higher risk of developing urinary incontinence than were those of the other breeds. The possibility that the urinary incontinence was due at least in part to other conditions must be considered, since eight of the bitches were 9 years or older before urinary incontinence occurred and seven of the incontinent bitches also had polyuria or polydipsia. There were no significant differences in the incidence of urogential problems listed above between the bitches of the ovariectomy and ovariohysterectomy group. It is hypothetized that a uterine disease such as CEH-endometritis cannot develop after complete ovariectomy, unless progestagens are administered. The results of this study indicate that ovariectomy does not increase the risk of CEH-endometritis or other complications in comparison with ovariohysterctomy.
It is concluded that there is no indication for removing the uterus during routine neutering in healthy bitches. On the contrary, ovariectomy should be considered the procedure of choice.

Source: Okkens, AC, Kooistra, HS, Nickel, RF (2003): Comparison of long-term effects of ovariectomy versus ovariohysterectomy in bitches
In: Der Praktische Tierarzt, 2003, Vol 84, Iss 2, pp 98-101


CANINE AND FELINE THERIOGENOLOGY is the only comprehensive, up-to-date textbook on small animal reproduction available. Veterinary management of normal reproduction and reproductive disorders in the male and female dog and cat are covered in detail, including such topics as sexual differentiation and normal anatomy, breeding management, use of chilled and frozen semen, pregnancy and parturition, neonatal care, clinical approach to infertility, and diseases of each of the reproductive organs. Some chapters address the pet overpopulation problem in the United States and approaches to population control in these species. This book is an invaluable resource to veterinarians, veterinary students, and others interested in companion animal reproduction.  See page 172 regarding OE vs OHE topics.

Canine and Feline Theriogenology

By Shirley Dianne Johnston, Margaret V. Root Kustritz, Patricia Schultz Olson

Edition: illustrated

Published by Elsevier Health Sciences, 2001

ISBN 0721656072, 9780721656076

592 pages


Should You OE or Should You OHE?

From Veterinary Practice News

By Phil Zeltzman, DVM, Dipl. ACVS
Dr. Phil Zeltzman is a small animal board-certified surgeon at Valley Central Veterinary Referral Center in Whitehall, Pa

Spays are one of the most common surgeries performed in veterinary practices. However common it is, this procedure has the strange propensity to generate heated discussions between advocates of the ovariectomy (OE) and proponents of the ovariohysterectomy (OHE).

So let’s try to stay away from the controversy and concentrate on the science.

Why is OE vs. OHE even a debate? It is based on the assumption that diseases of the uterus are prevented by removing it—no uterus, no future disease?


OE Preferred in Europe

This argument (“the assumption” above… TJD) doesn’t fly in Europe, where OE has been practiced for decades with reportedly no increased incidence of uterine disorders. The risk of uterine tumor in particular is extremely small (0.003 percent).1 In addition, the uterus atrophies after ovariectomy, which may further reduce the risk of disease.


Elizabeth Arnold Stone, a board-certified surgeon at the Ontario Veterinary College in Canada, writes in the last edition of Slatter’s Textbook of Small Animal Surgery: “There is no definitive advantage for removing the uterus in addition to the ovaries during routine neutering. Ovariectomy is less invasive and takes less time than ovariohysterectomy.”2


This also means that anesthesia is shorter with OE.

The complications are similar, although with OE, there is theoretically less risk of hemorrhage, which is the No. 1 complication with OHE. The risk of ovarian remnant syndrome is similar. The risks of urinary incontinence and weight gain are similar.


What about the current literature? This columnist was eager to review for Veterinary Practice News readers over 30 years worth of literature about the art of spaying. Luckily, a group recently did just that for us.


A team from the University of Utrecht in the Netherlands, led by van Goethem, performed an extensive review of scientific articles published from 1969 to 2004. The conclusion of the Veterinary Surgery article is fairly straight-forward: “There is no benefit and thus no indication for removing the uterus during routine neutering in healthy bitches. Thus we believe that OE should be the procedure of choice for canine gonadectomy.”3


First, Do No Harm

Van Goethem, et al, also write:


 “The surgeon has to choose the least invasive, fastest and safest procedure.” If we agree with that basic principle—reminiscent of the “First, do no harm” mantra—and as long as there are no medical contraindications, then it is difficult to argue that OHE is a better choice than OE in selected cases. 


Proponents of OE maintain that the risk of pyometra is minimal since the pet will no longer have heat cycles. Multiple long-term studies confirm this statement: Stump pyometra did not occur in any patient who had undergone OE.4


One concern of OHE advocates is that an OE patient exposed to progestagens—endogenous (tumors, ovarian remnant) or exogenous (medications for dermatological diseases)—may be at risk for pyometra. These risks are small, and there are safer alternative to progestagens for dermatological diseases.


Not Much Help

So we turned to officials to obtain an objective opinion. That didn’t really help.

  • The American Veterinary Medical Assn. doesn’t have an official policy. 
  • The American Animal Hospital Assn. doesn’t have an official position statement.
  • The Professional Liability Insurance Trust doesn’t dictate how veterinarians should practice.

The role of these organizations is not to tell us which procedure is better. It would seem that using the appropriate suture material, the adequate suture pattern, and optimal sterility and surgical techniques would fall under “standards of care” more than which procedure is better.

And of course, the surgery report should document information such as “single ligature” vs. “double ligature” vs. “transfixion,” and which suture material and pattern were used.


Burden of Proof

Should a legal issue arise, the pet owners would have the burden of proof. It would be their responsibility to find an expert willing to testify that procedure A should have been performed instead of procedure B. Likewise, it would be the pet owner’s responsibility to prove that negligence occurred and that standards of care were not met.

Then again, what are standards of care? Who defines them?

They seem to be a fairly vague and changing notion. They are certainly not “area-based” anymore, i.e. they don’t depend on what your local colleagues do. Rather, they are based on up-to-date procedures as defined by current publications, university professors and board-certified specialists.

In the case of OE vs. OHE, there seems to be ample information to document the risks and benefits of both procedures.

Besides, why couldn’t more than one standard of care exist for a medical procedure as long as it is scientifically and ethically acceptable?


Each practitioner should have the prerogative of deciding which procedure is better for each patient. This is no different than deciding which vaccination protocol makes the most sense, or which procedure is better to stabilize a torn ACL, or which suture pattern is ideal for a cystotomy, or which gastropexy technique is stronger for bloat, or which drug cocktail is safer for anesthesia.

It’s a judgment call.


So what’s a concerned practitioner to do? Here are a few suggestions:

  • Check with your state board to learn the current thought.
  • Tailor your treatment plan to each patient.
  • Communicate with the client. Go over the risks and benefits of each procedure.
  • Obtain a signed consent form from the well-informed client.
  • Document everything you do in your medical record and surgery report.

In the heat of the debate, one small word may have been missed. Van Goethem, et al, conclude: “Canine OE can replace OHE as the procedure of choice for routine neutering of healthy female dogs.” The key word is “healthy.”


If the uterus is healthy in a healthy, nongravid female spayed before her first heat, then performing an ovariectomy should be acceptable. If there is any doubt that the uterus may not be healthy, then an ovariohysterectomy is medically indicated.



1.    E. Arnold Stone, Textbook of Small Animal Surgery. Saunders, 2003, p. 1495.

2.    B. van Goethem, et al, “Making a rational choice between ovariectomy and ovariohysterectomy in the dog: A discussion of the benefits of either technique.” Veterinary Surgery. 2006, Vol. 35, No. 2, pgs. 136-143.

3.    L.A.A. Janssens, “Bilateral flank ovariectomy in the dog-surgical technique and sequelae in 72 animals.” Journal of Small Animal Practice, 1991, Vol. 32, No. 5, pgs. 249-252.

4.    L.M. Howe, “Surgical methods of contraception and sterilization.” Theriogenology, 2006, Vol. 66, No. 3, pgs. 500-509.

 T J Dunn, DVM