ArticlePDF AvailableLiterature Review

A literature review on the welfare implications of gonadectomy of dogs

Authors:
  • American Veterinary Medical Association
JAVMA • Vol 250 • No. 10 • May 15, 2017 1155
Small Animals
In the United States, dogs not intended for breeding
are routinely neutered via elective gonadectomy
(OHE or castration), resulting in 86% of owned dogs
being spayed or neutered.1 In addition to the fact that
gonadectomy renders dogs infertile, removal of sex
hormones produced by the gonads may influence the
incidence of a variety of disease processes. The risks
and benefits of gonadectomy are constantly being
examined, which has resulted in renewed conversa-
tions about if and when to neuter animals. This has
created a challenging environment for companion
animal practitioners striving to make the best deci-
sions for their patients.
In a joint position statement,2 the American Col-
lege of Theriogenologists and Society for Theriogenol-
ogy assert that companion animals not intended for
breeding should be spayed or neutered, although
the decision must be made on a case-by-case basis
and take into consideration the pet’s age, breed, sex,
intended use, household environment, and tempera-
ment. Developing recommendations for an informed
case-by-case assessment requires an evaluation of the
risks and benefits of gonadectomy, including potential
effects on neoplasia, orthopedic disease, reproductive
disease, behavior, longevity, and population manage-
ment as well as the risks of anesthetic and surgical
complications. However, many factors other than neu-
ter status play an important role in these outcomes,
including breed, sex, genetics, lifestyle, and body con-
dition. Potential consequences for an individual animal
must also be weighed with the necessity of managing
unwanted pet populations. Because of the aforemen-
tioned variables, there currently is no single recom-
mendation regarding gonadectomy that would be ap-
propriate for all dogs. The information reported here
summarizes the currently available literature involving
risks and benefits that might be considered when mak-
ing a recommendation about gonadectomy of dogs and
the optimal age for performing the procedure.
Considerations During Evaluation
of the Available Literature
Inconsistencies in patient categorization of vari-
ous studies make it difficult to synthesize the overall
A literature review on the welfare implications
of gonadectomy of dogs
Kendall E . Houlihan dvm From the Animal Welfare Division, AVMA, 1931 N Meacham Rd, Ste 100, Schaumburg,
IL 6 017 3.
Address correspondence to Dr. Houlihan (khoulihan@avma.org).
data set. Depending on the study, early gonadectomy
can be defined in a variety of ways, including surgery
prior to 5.5 months of age3,4 or before 1 year of age.5–7
Age at gonadectomy was unavailable for other stud-
ies8 –10 that differentiated only between sexually in-
tact and neutered dogs.
Many of the existing reports are retrospective
studies. Although the number of available cases is
often quite high, the source for the cases in a study
can result in an inherent selection bias. The VMDB
selects for patients cared for at referral hospitals, and
members of breed clubs may represent an extremely
different population than the animal population for
typical pet owners.11 Owners must elect to partici-
pate in surveys and also may have recall bias.12
Determining the incidence of diseases also pos-
es a major challenge. Veterinary medicine lacks the
population surveys used in human medicine to ob-
tain a baseline incidence within the general popu-
lation. Other than the VMDB, which contains cases
limited to some veterinary teaching hospitals, most
private, corporate, and specialty-referral practices
manage their records independently. Owner prefer-
ence or veterinarian recommendation may result in
patients being treated for a disease or being eutha-
nized without a definitive diagnosis. Additionally, the
information on incidence in pathology studies may
differ because some diseases may represent inciden-
tal findings and specimens are limited to owners who
elect for biopsy or necropsy.
The multifactorial nature of many diseases inter-
feres with determining the underlying reason why
there may be a link to neuter status or timing of go-
nadectomy.11 The etiology of many diseases is not de-
finitively known, which makes it difficult to evaluate
the potential effects of sex hormones. Furthermore,
detecting an association does not indicate causation.
A deeper understanding of how the presence or ab-
sence of sex hormones affects each disease process
is needed before more concrete conclusions can be
made about the influence of gonadectomy on overall
health.
Relative risk and OR serve as a measure of the
strength of the association between a disease and
exposure to a factor (in this case, gonadectomy).12
Relative risk is the ratio of 2 risks (usually the ratio
of the risk of disease in an exposed group to the risk
of disease in an unexposed group). It provides a mea-
sure of the strength of the association between the
disease and exposure to the factor. If the relative risk
is 1.0, then exposure to the factor does not affect an
animal’s chance of developing the disease; a relative
ABBREVIATIONS
BPH Benign prostatic hyperplasia
CCL Cranial cruciate ligament
OHE Ovariohysterectomy
VMDB Veterinary Medical Databases
1156 JAVMA • Vol 250 • No. 10 • May 15, 2017
Small Animals
risk > 1.0 indicates an increased risk for developing
the disease associated with exposure to the factor.
In contrast, the OR is the ratio of 2 odds (usually the
odds of disease in a group exposed to a factor divid-
ed by the odds of disease in an unexposed group). It
represents an estimate of the relative risk when the
disease is rare.
The importance of an increased relative risk must
be considered along with the overall prevalence of
the condition within the population.11 An increased
relative risk for a more common neoplasia such as
lymphoma has the potential for greater consequences
than does an increased relative risk for a rare disease
such as uterine neoplasia. Another example is the rar-
ity of prostate neoplasia in male companion animal
dogs, which effectively negates concerns a veterinar-
ian might have that neutering of male dogs will cause
prostate neoplasia.13
In addition to the frequency of disease, severity
of the disease and availability of effective treatments
are also considerations when weighing the risks and
benefits of gonadectomy for an individual animal. Po-
tentially increasing the likelihood of an easily man-
aged disease process such as urinary incontinence
is outweighed by the desire to minimize risk for the
development of mammary gland neoplasia. Practitio-
ners also must consider potential effects on overall
quality of life as well as morbidity and mortality rates.
Breed-specific studies are valuable to veterinari-
ans who work with those breeds, but the information
cannot be extrapolated and applied to all dogs.11 Con-
trary to the association between neoplasia and gonad-
ectomy in Golden Retrievers, there is not a significant
correlation between neutering male or female Labra-
dor Retrievers or German Shepherd Dogs at any age
and the development of several neoplasms (lympho-
sarcoma, hemangiosarcoma, or mast cell tumor).5,6 ,14
Further research focusing on specific breeds and
also on broader groups of dogs will be important for
making recommendations about individual patients.
Currently, it is important to acknowledge the large
role that genetics and breed play in disease processes
when developing recommendations.15,16
Breeding practices may also impact the data. Ani-
mals with an increased incidence of neoplasia, ortho-
pedic disease, or undesirable behaviors may be less
likely to be chosen as stud dogs. As a result, those
dogs and their offspring that are at higher risk geneti-
cally may be neutered to prevent passage of the dis-
ease risk to progeny.
Neoplasia
Neoplasia represents a major cause of morbidity
and fatalities for companion animals and is a leading
cause for concern among dog owners.16–1 8 Factors
contributing to the development of neoplasia may in-
clude, but are not limited to, genetic predisposition,
breed, age, viral infection, environment, chronic in-
flammation, and neuter status. Gonadectomy has the
potential to decrease the incidence of certain types of
neoplasia and increase the incidence of others. When
the risks and benefits of gonadectomy related to neo-
plasia are evaluated, consideration must be given to
the morbidity and mortality rate for each neoplastic
disease as well as its prevalence within the general
canine population or a specific breed.
Mammary gland tumors are the most com-
mon neoplasia in female dogs.16,19–2 3 The incidence
of mammary gland neoplasia in dogs in the United
States (3.4%) is significantly lower than that in other
countries in which OHE is typically used only as a
treatment of uterine diseases in older dogs.19,21,23–28
For instance, mammary gland neoplasia accounted
for 70% of all cases of neoplasia evaluated in the mu-
nicipality of Genoa, Italy, between 1985 and 2002,
and the incidence of malignant mammary gland tu-
mors in Norway was 53.3%.21,23
Because 35% to 51% of mammary gland tumors
of dogs are malignant, they represent the most com-
mon malignant tumors in dogs.20 ,2 8 –31 In addition
to local invasion and ulceration of primary tumors,
malignant tumors have the potential to metastasize,
most commonly to the regional lymph nodes and
lungs.19,28 ,29, 31,32 This combination of a high incidence
and malignancy represents a substantial risk to the
female canine population. Age, hormonal exposure,
and breed are the 3 main factors that contribute
to the risk of developing mammar y gland tumors,
whereas diet, body weight, and obesity may play
smaller roles.19,24,30,33
Breed influences the incidence of mammary
gland neoplasia.16,21,25,29,30,34,35 These reports are sup-
ported by more recent breed-specific literature. In a
retrospective study5 conducted to evaluate Golden
Retrievers and the follow-up study6 conducted to
compare results for Golden Retrievers and Labrador
Retrievers, extremely few dogs had mammar y gland
neoplasia regardless of neuter status. This could have
been affected by the age of patients included in the
studies because the mean age for development of ma-
lignant mammary gland tumors is approximately 9 to
11 y e a r s ,11,24,28,35 and the 2 aforementioned studies5,6
only included patients up to 8 years of age. However
in retrospective studies focusing on Vizslas36 and Ger-
man Shepherd Dogs14 through at least 11 years of age,
mammary gland neoplasia remained much less com-
mon than the other neoplasias.
Compared with spayed bitches, sexually intact fe-
males have a higher incidence (3 to 7 times as high)
of mammary gland tumors.33,35 Historically, there has
been general agreement that spaying has the greatest
benefit for prevention of mammary gland tumors if
performed prior to the first estrus. A protective effect
of OHE is indicated by the fact that the relative risk
of mammary gland tumors for bitches spayed before
their first estrus is 0.05%, compared with that for sexu-
ally intact bitches, which then increases to 8% when
spayed after the first estrus and 26% when spayed
after the second estrus.37 Subsequent studies20,30,38,39
have continued to support the protective effect of
JAVMA • Vol 250 • No. 10 • May 15, 2017 1157
Small Animals
early spaying. The connection between exposure to
exogenous progesterone and an increased risk of de-
veloping malignant mammary gland tumors further
supports the association.11,40 Hormonal influences
from pregnancy or estrus beyond the initial 2 estrous
cycles have not been found to significantly contribute
to an increased risk of malignant mammary gland tu-
mors.19,34,37 Recently, the protective benefit of spaying
was challenged when a systematic review of the re-
lated literature was unable to identify a strong associa-
tion between spaying and development of mammary
gland tumors.41 However, that review was based on
meta-analyses in human medicine, which required a
massive body of literature that currently does not exist
in veterinary medicine11,42 ; thus, the review41 of spay-
ing and development of mammary gland tumors may
have reflected a lack of statistical power in the analysis.
Ovarian tumors of the bitch are uncommon,
although it has been difficult to determine the inci-
dence in part because of the routine practice of OHE
in the United States.1,43–47 The overall prevalence of
ovarian tumors reported is 0.5% to 1.4%44–47 but is po-
tentially as high as 6.25% when including histologic
evaluation.46,4 8 Age of occurrence, rate of metastasis,
and frequency of concurrent uterine malignancy or
endocrine disease are dependent on the type of neo-
plasia.44–47,49 Ovariectomy or OHE would be preven-
tive and is the mainstay of treatment, but gonadec-
tomy would only be helpful for benign or localized
ovarian tumors.11,43 The prognosis is poor for patients
with malignant neoplasia with evidence of metastatic
disease, which can occur in up to 50% of cases.44,49
Uterine neoplasms are rare, accounting for 0.3%
to 0.4% of all neoplastic conditions in dogs; benign
mesenchymal tumors and leiomyomas are the most
common types of uterine neoplasms.29,43,50,51 Leiomy-
omas are generally slow growing, noninvasive, and
nonmetastatic.43,50 Because most uterine neoplasms
in dogs are benign, OHE is the treatment of choice
and often is curative.29,4 4
Vaginal and vulvar tumors account for 2.4% to 3%
of all tumors of dogs.44,51,52 Leiomyomas are the most
common vaginal tumors of dogs.34,44,50 Because they
most commonly develop in sexually intact bitches,
it is suggested that vaginal leiomyomas may be hor-
mone dependent.44,50 Although this association has
not been proven, OHE may have a substantial sparing
effect. For benign tumors, OHE used as an adjunct
treatment to surgical excision of the primary vaginal
or vulvar tumor is almost always curative.34,43,44,50,51
Transmissible venereal tumors of dogs are trans-
mitted primarily by coitus.53–55 Consequently, free-
roaming sexually intact dogs are at greatest risk.54,55
In enzootic areas where breeding is poorly controlled
and there are high numbers of free-roaming sexually
active dogs, transmissible venereal tumor is the most
common tumor of dogs.53–55 Transmissible venereal tu-
mors generally remain localized to the external geni-
talia.53–55 Tumors can become locally invasive, and me-
tastasis occurs in up to 5% to 17% of affected dogs.54,55
A decrease in mating behavior within a population as
a result of gonadectomies would greatly reduce the oc-
currence of transmissible venereal tumors.
Testicular tumors are a common neoplasia, ac-
counting for up to 16% to 27% of tumors of sexually
intact male dogs and approximately 90% of all tumors
in the male reproductive tract.56–60 Unilateral testicu-
lar enlargement with atrophy of the contralateral testis
is often evident, but metastasis is rare.2 8,5 6, 61 Bilateral
castration serves as both a preventive measure and the
treatment of choice for most testicular tumors and is
typically curative.11,43,50,57,61 Because cryptorchidism is
hereditary and intra-abdominal cryptorchid testes are
strongly associated with testicular neoplasia, cryptor-
chid dogs should be castrated.43,57,58,60,61
Prostatic carcinoma of dogs is aggressive and
characterized as locally invasive with high metastatic
potential.43,50,62 Although prostate neoplasia is seen
more often in dogs than in other domestic species,
prostate neoplasia is considered rare in dogs, with an
estimated prevalence of 0.29% to 0.6%.11,13,16,43,63–66
In the past, castration was recommended as part of
treatment and viewed to have the potential to de-
crease the risk of prostatic carcinoma.34,50,63 More re-
cent studies13,67,68 have shown castration to be a risk
factor for development of prostate neoplasia in male
dogs, with the OR ranging between 3.6 and 4.34 for
prostatic carcinoma. The age at castration may not
have an effect on when prostatic carcinoma develops
because the interval between castration and onset
of prostatic problems is highly variable.67 Also, the
age at which prostate neoplasia was diagnosed was
older for neutered dogs or did not differ significantly
between sexually intact and neutered dogs.13,67 Risk
of developing prostate neoplasia also differs among
breeds.13,34, 67
Although tumors of the bladder and urethra are
rare in dogs, accounting for approximately 2% of neo-
plasms in dogs, invasive transitional cell carcinoma
is the most common type.43,69–73 Transitional cell
carcinomas in dogs are highly malignant, and local
metastasis is common.43,69 Associations have been
made between these tumors and breed, female sex,
obesity, environmental factors, and possibly cyclo-
phosphamide.16,43,69,70,72–75 Gonadectomy also appears
to increase the risk for developing transitional cell
carcinomas, although the reason for this increase
has not been determined.13,69,71,7 2 For neutered male
dogs, the relative risk for the development of tran-
sitional cell carcinomas of the urinary bladder and
prostate was found to be 3.56 and 8.00, respectively,
compared with the relative risks for sexually intact
male dogs.13 Investigators of a retrospective study71
of 155 dogs reported that gonadectomized dogs were
at an increased risk (OR, 2.03) of developing tumors
of the lower urinary tract. The prognosis for the pa-
tients evaluated in that study was poor, with only 16%
surviving 1 year. Most dogs were untreated and eu-
thanized at the time of neoplasia diagnosis or subse-
quently died of the disease.71
1158 JAVMA • Vol 250 • No. 10 • May 15, 2017
Small Animals
Lymphoma is one of the most commonly diag-
nosed neoplasias of dogs.16,23 ,76 –7 9 The prognosis for
individual dogs differs widely. Although rarely cur-
able (< 10% of cases), complete remission can be
achieved with conventional chemotherapy in 60% to
90% of affected dogs.76,7 7,79,8 0 Good quality of life is
typically maintained during extended remissions of
6 to 13 months.76 ,7 7,8 0 Associations have been made
between the development of lymphoma and breed as
well as environmental, immunologic, and hormonal
factors; however, the etiology is likely multifactorial
and largely unknown.16,76 ,77,79, 81,8 2 With regard to go-
nadectomy as a risk factor for lymphoma, a compara-
tive medicine study82 that involved use of data in the
VMDB revealed that sexually intact male dogs and
neutered male and female dogs were twice as likely
as sexually intact female dogs to develop lymphoma.
Similar results have been reported in human medi-
cine, with men developing non-Hodgkin’s lympho-
ma approximately 50% more often than women.11,82
However, this association was not evident for the
evaluation of the Animal Tumor Registry of Genoa,
Italy, which revealed similar incidence rates of non-
Hodgkin’s lymphoma in male and female dogs.23 Mul-
tiple breed-specific studies have related but incon-
sistent findings. For Vizslas, analysis suggested that
both neutered males and females were 4.3 times as
likely as their sexually intact counterparts to have
lymphoma.36 Sex was not found to be a risk factor for
Vizslas irrespective of neuter status.36 Gonadectomy
of either sex did not affect the risk of lymphoma in
Labrador Retrievers or German Shepherd Dogs.6 ,14
In Golden Retrievers, there was not a significant risk
of developing lymphoma associated with spaying fe-
males at any age.5 Male Golden Retrievers neutered
before 1 year of age were 3 times as likely as sexually
intact males to develop lymphoma, but there were no
cases of lymphoma in the group of male dogs neu-
tered at > 1 year of age.5
Mast cell tumors comprise 16% to 21% of all cuta-
neous tumors of dogs.8,27,78,83,84 Patient prognosis dif-
fers and is dependent on multiple factors, including
histologic grade, tumor location, breed, and clinical
stage of the disease at the time of diagnosis.16,84– 88 Al-
though there is no apparent sex predilection, there
is evidence that spayed females may have a higher
relative risk of developing a mast cell tumor, com-
pared with the likelihood for their sexually intact
counterparts.8,11,83,87 Investigators of a study8 of dogs
examined at the Animal Medical Center in New York
reported an OR of 4.11 for spayed females to develop
mast cell tumors, compared with the likelihood for
sexually intact bitches, although the age at gonadec-
tomy was unknown for that study. The odds of go-
nadectomized Vizslas of either sex developing mast
cell tumors were 3.5 times the odds of sexually intact
Vizslas developing mast cell tumors.36 For Golden
Retrievers,5 Labrador Retrievers,6 and German Shep-
herd Dogs,14 there was not a significant difference be-
tween the incidence of mast cell tumors in males and
females regardless of neuter status or time of gonad-
ectomy. There are several breeds at an increased risk
for developing mast cell tumors regardless of neuter
status.16,83,84
Hemangiosarcoma represents approximately 5% to
7% of all noncutaneous primary malignant neoplasms of
dogs.16,3 0,78 ,8 9 The overall prognosis for dogs with hem-
angiosarcoma is extremely poor, with 10% surviving
for 12 months, even when receiving adjunctive chemo-
therapy after surgery.89–92 Although age at gonadec-
tomy was unknown, a retrospective study9 of splenic
hemangiosarcoma and hematoma in various breeds
revealed that spayed females have a significantly in-
creased likelihood of developing hemangiosarcoma
(OR, 2.2) when compared with the likelihood for sexu-
ally intact female dogs.
Hemangiosarcoma has also been evaluated in
multiple breed-specific retrospective studies. Neuter
status of male Golden Retrievers5 and Vizslas36 did not
affect the overall likelihood of developing hemangio-
sarcoma. However, when only male Vizslas neutered
at > 12 months of age were considered, they were 5.3
times as likely to develop hemangiosarcoma.36 This
increased risk in only late-gonadectomy dogs was
mirrored in female Golden Retrievers spayed at > 1
year of age.5 Those late-spayed females had heman-
giosarcoma > 4 times as frequently as did sexually
intact females and females spayed before 6 months of
age.5 Reasons that dogs neutered before 1 year old and
sexually intact dogs have a similarly reduced risk for
hemangiosarcoma, compared with the risk for female
dogs neutered at > 12 months of age, are still being
debated. Female Vizslas spayed at > 12 months of age
had a higher risk (OR, 11.5) of developing hemangio-
sarcoma, compared with the risk (OR, 6.0) for those
spayed before 12 months of age.36 This was a signifi-
cant increased risk for both groups of spayed Vizslas,
compared with the risk for sexually intact females,
which is in contrast to the results for Golden Retriev-
ers.5 It is important to mention that neuter status for
Golden Retrievers and Labrador Retrievers of both
sexes was not associated with a significant increased
risk of developing hemangiosarcoma in a follow-up
comparative study.6 Gonadectomy also is not a risk
for the development of hemangiosarcoma in Ger-
man Shepherd Dogs.14 Cardiac hemangiosarcoma
was specifically evaluated in a retrospective study93
that included data from the VMDB. In that study,93
gonadectomized males and females of various breeds
had overall relative risks of 1.6 and 4.38, respectively,
compared with that of their sexually intact counter-
parts. The incidence of cardiac tumors in the total
population was 0.19%.93
Osteosarcoma is the most common primary ma-
lignant bone tumor of dogs.16,94 –99 Osteosarcoma is lo-
cally aggressive and frequently has early metastasis,
most often to pulmonary structures.94,95,98–100 Meta-
static disease is often subclinical and only apparent
radiographically in < 15% of patients at initial exami-
nation.94,95,98–100 Treatment can be intensive and often
JAVMA • Vol 250 • No. 10 • May 15, 2017 1159
Small Animals
includes adjunctive therapy because approximately
90% of patients die of metastatic disease within 1
year when amputation is the only treatment.94,95,98–100
Large- and giant-breed dogs are at greater risk of de-
veloping osteosarcoma.10,16,94,98,99 Gonadectomy may
also contribute to a higher risk of developing osteo-
sarcoma.7,10 A retrospective study10 conducted with
data from the VMDB confirmed that increasing breed
size is a significant risk factor for osteosarcoma. Al-
though age at gonadectomy was not available, gonad-
ectomized dogs were twice as likely as sexually intact
dogs to develop osteosarcoma.10 A historical cohort
study7 for which investigators specifically evaluated
Rottweilers revealed that risk for osteosarcoma was
significantly influenced by both neuter status and age
at gonadectomy. Male and female dogs that were neu-
tered before 1 year of age had a risk that approximate-
ly 1 in 4 would develop osteosarcoma during their
lifetime.7 Furthermore, there is potentially an inverse
association between lifetime exposure to gonadal
hormones and risk of spontaneously developing os-
teosarcoma because dogs that developed osteosarco-
ma in that study7 were sexually intact for significantly
fewer months than were dogs that did not develop
osteosarcoma. Neuter status or age at gonadectomy
does not affect development of osteosarcoma in Ger-
man Shepherd Dogs.14
Orthopedic Diseases
Musculoskeletal diseases such as CCL disease and
hip dysplasia are not inherently life-threatening con-
ditions, but they do affect physical performance and
quality of life of patients. Surgical correction of CCL
disease and hip dysplasia can also be cost prohibitive
for owners. In situations whereby chronic orthope-
dic pain of animals cannot be adequately managed,
especially in large-breed dogs, euthanasia may be
considered. The incidence of CCL disease and hip
dysplasia is 1.7% and 1.8%, respectively.28 The true
disease prevalence of hip dysplasia is difficult to de-
termine because of selection bias for those dogs pro-
vided for evaluation or that are typically screened,
membership bias for the groups of the canine popula-
tion being considered, and differences in case defini-
tion when determining a positive result.101 This could
result in a gross underestimation of the prevalence
within the general canine population or within spe-
cific breeds.101
Gonadectomy is a risk factor for development of
CCL disease and hip dysplasia in both male and female
dogs.102–105 The complex pathophysiologic processes
of these orthopedic diseases make it challenging to
connect cause and effect.105 Although heritability is
the primary factor for the development of hip dys-
plasia, it is a multifactorial condition.106 Hip dysplasia
most commonly affects large-breed dogs. Similarly,
most dogs treated for CCL disease are young, active,
large-breed dogs.106 Development of CCL disease
may result from degenerative or traumatic causes.106
Ligament degeneration has also been associated with
aging, conformational abnormalities, and immune-
mediated arthropathies.106
Investigators of 1 study102 found an overall preva-
lence for CCL disease of 3.48% , with gonadectomized
dogs having a significantly higher prevalence than
their sexually intact counterparts, and neutered fe-
males having the highest prevalence. This supported
results of another study105 that revealed an increased
prevalence of CCL disease in female dogs and that
the age at the time of OHE did not appear to be a
factor. The finding that large dogs were more likely
to have CCL rupture is consistent throughout several
studies.102,103,10 5 A retrospective study103 conducted to
evaluate both musculoskeletal diseases found that go-
nadectomy increased the prevalence of CCL disease
in male and female dogs and that hip dysplasia was
more prevalent among neutered male dogs and less
common among female dogs regardless of their neu-
ter status.
Breed predisposition may also play a major role
in the development of CCL disease and hip dyspla-
sia.5,6,14,101,10 3–105 ,107 Four breed-specific studies5,6 ,14,107
revealed a significant increase in orthopedic disor-
ders in gonadectomized dogs, compared with results
for their sexually intact counterparts, although the
incidence differed widely among breeds. Prepuber-
tal gonadectomy of Golden Retrievers resulted in an
increased incidence of joint disorders (3 to 5 times
as high as the incidence for sexually intact dogs),
whereas prepubertal gonadectomy of Labrador Re-
trievers was associated with an incidence that was
twice as high as that for sexually intact dogs. The in-
cidence of hip dysplasia increased significantly only
in male Golden Retrievers neutered before 1 year
of age. Elbow joint dysplasia increased significantly
only for male Labrador Retrievers neutered before 6
months of age (incidence, 2%), compared with that
for sexually intact males (incidence, 0.57%).5,6 Boxers
that were gonadectomized at least 6 months prior to
diagnosis of hip dysplasia, (mean age at gonadectomy,
3 years) were 1.5 times as likely as sexually intact Box-
ers to develop hip dysplasia. Male and female German
Shepherd Dogs gonadectomized before 12 months of
age were at an increased risk for CCL tears, compared
with the risk for those remaining sexually intact.14
There was not a significant association between go-
nadectomy and hip dysplasia or elbow joint dysplasia
in German Shepherd Dogs.14 Prepubertal gonadecto-
my is associated with increased bone length attribut-
able to delayed closure of growth plates.108 Although
it has been speculated that this subsequently leads
to the development of certain orthopedic diseases,
the speculated association has not been explained or
confirmed.14,15 ,2 8 ,3 4
The effect of sex hormones on orthopedic disease
has also been explored via comparisons between go-
nadectomy performed at early and traditional ages.3,4
Comparison of outcomes for shelter dogs gonadecto-
mized before or after 24 weeks of age revealed no
association between age at gonadectomy and fre-
quency of musculoskeletal problems during the 4
1160 JAVMA • Vol 250 • No. 10 • May 15, 2017
Small Animals
years a fter gonadectomy. A few dogs developed hip
dysplasia, but they did not require surgical or prolonged
medical management.3 A similar study4 for which fol-
low-up monitoring was available for as long as 11 years
after gonadectomy revealed a significant increase in the
incidence of hip dysplasia among dogs gonadectomized
before 5.5 months of age, compared with the incidence
for those gonadectomized after 5.5 months of age. How-
ever, there was a lower rate for euthanasia among the
early-age gonadectomized dogs with hip dysplasia.4 Al-
though neither of these studies included a comparison
with sexually intact animals and it was unclear as to the
diagnostic tests used to diagnose hip dysplasia, the low
incidence and severity of orthopedic problems in pre-
pubertally gonadectomized dogs makes it worthwhile
to consider early-age neutering.3,34
Behavior
Inappropriate or unacceptable behaviors dis-
rupt the human-animal bond and are one of the most
common reasons for relinquishment or rehoming of
dogs.3,10 9 Because some owners pursue gonadectomy
to prevent or resolve behavioral problems of their
pets,15,110 –112 they should be given realistic expecta-
tions for potential postsurgical behavioral changes.
Gonadectomy and the resultant decrease in gonadal
steroid hormones typically result in a marked reduction
or elimination of sexually dimorphic behaviors, includ-
ing roaming, hormonal aggression (fighting with other
males or females), and urine marking.2,15, 28 ,2 9,110 ,112 –114 In
males, the age at castration or duration of the behavior
does not change the likelihood that surgery will alter
these unwanted behaviors.113,114
The literature provides consistent results regard-
ing the effects of gonadectomy on behaviors driven
by testosterone or estrogen; however, studies involv-
ing behaviors not directly related to gonadal steroid
hormones have resulted in mixed findings. Although
the most serious bite injuries in the United States in-
volve sexually intact dogs,115 gonadectomy has not
been found to be a useful measure to prevent ag-
gressive behavior in male or female dogs.109,111,116 ,117
Gonadectomy consistently reduces only intermale
aggression and may actually contribute to increased
aggression in female dogs.109, 111,116 –118 In a study118
conducted to evaluate canine patients referred for
management of behavioral problems, sexually intact
males and neutered females were significantly more
likely to be referred because of aggression and stimu-
lus reactivity than were neutered males and sexually
intact females. A prospective controlled study117 of
German Shepherd Dogs revealed increased reactiv-
ity to unfamiliar people and unknown dogs follow-
ing OHE performed between 5 and 10 months of age,
compared with results for dogs allowed to remain
sexually intact. A study116 based on responses of 150
owners of dogs to questionnaires administered at the
time of spaying and again 6 months later revealed a
significant increase in dominance aggression toward
family members by bitches following OHE, compared
with the response of sexually intact female dogs of
similar age and breed assessed at the same time peri-
ods. Female puppies that already had displayed signs
of aggression were at highest risk for an increase in
dominance aggression following gonadectomy, and
there was little risk of increased aggression in older
dogs that had not already displayed aggressive behav-
ior.116 Therefore, consideration should be given to
postponing OHE in female puppies with a history of
aggression.
Differences in study designs and results create ad-
ditional challenges when the potential consequences
of gonadectomy on behavior are evaluated. Investiga-
tors of 1 study110 reported decreased activity in 50%
of male dogs neutered as adults, contrary to results
of an earlier study113 in which there was no indica-
tion that neutered male dogs become more inactive
or lethargic. Additional differences were for dogs go-
nadectomized at 7 weeks or 7 months of age, which
were judged to be more excitable than were sexually
intact dogs.108 When dogs gonadectomized before or
after 5.5 months of age were compared, those neu-
tered before 5.5 months of age were more likely to
display noise phobias and sexual behaviors. How-
ever, separation anxiety, urination due to fear, and
the likelihood a dog would escape were less likely.4
Male puppies neutered prior to 5.5 months of age had
increased aggression toward family members and
also were more likely to bark excessively at visitors
or household members.4 In another study3 conducted
to evaluate gonadectomy in dogs before or after 24
weeks of age, investigators concluded that there was
no increase in the incidence of behavioral problems
or return rate to shelters for prepubertally gonadecto-
mized dogs. Vizslas gonadectomized before 6 months
of age reportedly have an increase of undesirable be-
haviors related to fear and anxiety.36 Investigators of
that study36 did not evaluate sexual behaviors such as
mounting and urine marking. When bitches of vari-
ous breeds spayed between 2 and 4 years of age were
compared with a sexually intact control group, no
behavioral differences were observed during the 2
months after gonadectomy.119
Interpretation of the literature related to behav-
ioral changes after gonadectomy is further compli-
cated by various definitions of aggression as well as
comparisons of similar-appearing but potentially un-
related behaviors (eg, aggression, reactivity or energy
level, and excitability).120 It is also possible that go-
nadectomy was recommended for some dogs as part
of a behavior treatment plan, which would artificially
increase the number of spayed or neutered dogs with
behavioral problems.28 Because of these complicating
factors, additional research is needed before conclu-
sions can be confidently made about the effects of
gonadectomy beyond the reduction of reproductive
behaviors. Specific evaluation of potential behavioral
consequences of surgery during critical periods of
behavioral development could help guide general
recommendations on the most appropriate time for
gonadectomy of puppies.120–123
JAVMA • Vol 250 • No. 10 • May 15, 2017 1161
Small Animals
Other Medical Implications
Gonadectomy can contribute to the prevalence
(or be used in the management) of a variety of medi-
cal concerns. In male dogs, castration helps prevent
androgen-related diseases, including BPH, chronic
prostatitis, perianal adenomas, and perianal herni-
as.28 ,2 9,34 ,124,12 5 Benign prostatic hyperplasia is the most
common prostatic disorder among sexually intact
male dogs, potentially affecting 50% of sexually intact
dogs by 5 years of age and 95% to 100% of sexually
intact dogs > 9 years old.29,3 4,6 6,12 4,125 Dogs with BPH
are predisposed to prostatic cysts, prostatitis, and pros-
tatic abscesses.66 ,67,124,125 In a study67 of multiple pros-
tatic disease processes, BPH was found to be by far the
most common prostatic abnormality associated with
clinical signs of prostatic disease. Signs of prostatic
disease most often include urethral discharge, hematu-
ria, or tenesmus.6 6,124 ,125 Castrated dogs accounted for
only 6.7% of the dogs with a nonmalignant prostatic
disorder (OR, 0.28).67 Castration is the recommended
treatment for most dogs with clinical BPH and results
in a decrease in the size of the prostate, regression of
clinical signs, and a reduced likelihood of developing
infectious prostatitis.28,29, 34, 61,67,124,1 25 The prognosis fol-
lowing castration is excellent.29
For females, other benefits of OHE include preven-
tion and treatment of disorders of the reproductive
tract, including pyometra, metritis, and ovarian cysts
as well as conditions associated with pregnancy and
parturition (eg, dystocia).15,2 9,3 4 ,12 6 Pyometra is a po-
tentially life-threatening condition often associated
with cystic endometrial hyperplasia.29 In countries
in which OHE is not as routinely performed as in the
United States, the mean incidence of pyometra can be
23% to 24% of dogs by 10 years of age.127 In a study46
that involved examination of ovarian tumors, 43% of
the dogs had a medical history consistent with pyome-
tra. Similar to other disease processes, the incidence of
pyometra may differ among breeds.6,127,128 An OHE is
the recommended treatment for pyometra in most cas-
es because medical management may not completely
clear infection and cannot reverse cystic endometrial
hyperplasia.127,128 Furthermore, subsequent estruses
could result in recurrent pyometra (estimated rate,
20%29 or 10% to 77%128). Septic shock and renal failure
are potential sequelae of pyometra.29,128 Mortality rates
of 4.2% to 4.3%127 and 0% to 17%28 have been reported
for dogs. Emergency treatment of pyometra also neces-
sitates unexpected and potentially substantial finan-
cial commitments by owners.
Acquired urinary incontinence is consistently cit-
ed as a potential sequela to spaying female dogs. Uri-
nary incontinence typically develops 3 to 5 years af-
ter gonadectomy.129 –132 It affects 2% to 20% of spayed
females and occurs most often in larger dogs.129–132
Females spayed before 3 months of age have the
highest risk of developing urinary incontinence that
requires medical treatment.4,131 Spaying females be-
tween 4 and 6 months of age does not appear to in-
crease the risk for urinary incontinence, compared
with the risk for those spayed after the first estrus.4,131
Age at gonadectomy may also influence time to onset
of urethral incompetence, with a shorter interval to
incontinence reported for bitches spayed when they
were older.132
A breed-specific study21 on German Shepherd Dogs
found that urinar y incontinence was considerably less
likely to develop in sexually intact females. However,
this was only a significant effect when sexually intact
females were compared with female dogs spayed be-
tween 6 and 11 months of age. The author’s conclusion21
that dogs spayed before 6 months of age or considered
as a group spayed prior to 12 months of age were not
at an increased risk for the development of urinary in-
continence conflicts with the previously reported4,14
increased risk attributable to early-age gonadectomy.
Although the information from that study21 supports
the association between gonadectomy and acquired uri-
nary incontinence, it may complicate recommendations
regarding the most appropriate age at which to spay a
German Shepherd Dog.
Urinary incontinence can negatively affect some
owner-animal relationships; however, it is impor-
tant to mention that none of the female dogs with
urinary incontinence in studies4,131 on early-age go-
nadectomy were relinquished to a shelter or given
to another owner, and the euthanasia rate of these
dogs was not higher than the overall euthanasia rate.
This may be because patients typically respond well
to medical management or because urinary inconti-
nence may not be viewed by owners as a sufficient
inconvenience or impairment to consider relinquish-
ment.3,28 ,130–133 Investigators of a recent systematic re-
view134 categorized the causal relationship between
gonadectomy and urinar y incontinence as weak.
However, similar to the previously mentioned sys-
tematic review on mammary gland neoplasia and go-
nadec to m y,41 information must be weighed with the
acknowledgment that a lack of qualifying literature
will negatively impact the statistical power of such a
systematic analysis.
It is estimated that obesity affects 24% to 30% of
the pet population in the United States.135 Retrospec-
tive studies28,136 have consistently found an increase
in body condition in dogs after gonadectomy. This ap-
pears to be a result of both an increase in appetite and
changes in metabolism.137 It is unclear whether age at
gonadectomy plays a major role in the risk of a neu-
tered dog becoming overweight, but there appears to
be an increased risk, compared with that for sexually
intact dogs, for patients primarily from 2 months to 2
years after surger y.4,119,136 Although obesity remains a
challenge in companion animal medicine, it is a mul-
tifactorial problem, and responsible management of
diet and exercise can maintain appropriate body con-
dition regardless of neuter status.2 8,34
Lifespan
Overall, gonadectomy appears to be associated with
an increase in lifespan.15,34,38,138–140 This has great impor-
1162 JAVMA • Vol 250 • No. 10 • May 15, 2017
Small Animals
tance for veterinary medicine, whereby euthanasia is
considered when quality of life is substantially compro-
mised and cannot be expected to reasonably improve. A
retrospective study38 that included data from the VMDB
found that neutering was strongly associated with an
increased lifespan (life expectancy of spayed females
was increased by 26.3%, and that of castrated males was
increased by 13.8%). Although gonadectomy increased
the risk of death attributable to neoplasia (except for
mammary gland neoplasia, which had a significantly
lower prevalence) and immune-mediated disease, it de-
creased the risk of death attributable to other causes,
including infectious disease and trauma.38 Similarly,
analysis of patient data evaluated in a 2013 report138 that
included data from primary care veterinary hospitals re-
vealed that spayed dogs typically lived 23% longer and
neutered dogs lived 18% longer than did sexually intact
female and male dogs, respectively. That report138 also
revealed that sexually intact dogs were more than twice
as likely as gonadectomized dogs to be hit by a car or bit-
ten by another animal. Results of a survey of owners of
> 3,000 British dogs indicated that spayed females lived
significantly longer than did males and sexually intact
females.139
For military working dogs, neutered males lived sig-
nificantly longer than sexually intact males and spayed
females.140 The study population did not have any sexu-
ally intact female dogs for comparison, and the age at
gonadectomy was not considered. Degenerative joint
disease of the appendicular skeleton and neoplasia were
the leading causes of death or reasons for euthanasia,
affecting 19.2% and 18.3% of the population of militar y
working dogs, respectively.140 Deaths associated with
gastric dilatation–volvulus (9.1% of the population) re-
sulted in an OR twice as high for gonadectomized males
and females as for sexually intact males. This differed
from results of other studies141,14 2 that indicated the risk
of gastric dilatation–volvulus was not associated with
neuter status. Lifespan, cause of death, and reason for
euthanasia differ among breeds.140
A retrospective study143 conducted to evaluate
necropsy data from dogs revealed that the mean age
at death did not differ significantly between gonad-
ectomized and sexually intact dogs of both sexes.
However, there were marked differences in longevity
among breeds.143 Gonadectomized male and female
Rottweilers lived longer than sexually intact Rottwei-
lers in a cohort evaluated for osteosarcoma,7 but a
separate longevity study144 found that females spayed
after 4 years of age were more likely to reach 13 years
of age. Although the retrospective cohort study36 of
Vizslas found significantly higher odds that gonad-
ectomized dogs would have neoplasia than would
sexually intact Vizslas, that same study did not reveal
a significant difference in longevity or age at death
between sexually intact and gonadectomized dogs.
Population Management
The AVMA concludes that dog and cat population
control is a primary welfare concern of society.145
There have been improvements in many geographic
areas, but the population of dogs in the United States
still substantially exceeds the capacity of society to
care and provide homes for all of them.145 It is estimat-
ed that millions of dogs are euthanized at animal shel-
ters in the United States each year, and over half of ca-
nine litters in US households are unplanned.4,15,28 ,146
Reducing unplanned and indiscriminant breeding
through gonadectomy is an effective means of non-
lethal population management.2 ,145, 147,148 Society ben-
efits from elective gonadectomy because animal over-
population is reduced, which results in fewer animals
relinquished to humane organizations.28 Local ordi-
nances regulating gonadectomy of dogs must also be
considered.
Ownership and the population of animals play
a role in the assessment for the appropriateness of
gonadectomy.11,145 It is imperative that dogs rehomed
through humane organizations do not contribute
further to overpopulation.145 Un for t u n ate l y, non-
compliance with spay-neuter contracts is as high as
60%.15,28 ,14 6 Gonadectomy performed before a dog
reaches sexual maturity or is adopted can address the
issue of owner compliance, ameliorate animal over-
population, and prevent the birth of unintended lit-
ters.4,14 7–149 Analysis of the current literature reveals
that there is minimal risk for surgical complications
or subsequent developmental abnormalities between
pediatric gonadectomy performed on dogs between
6 and 14 weeks of age and gonadectomy performed
on dogs at the more traditional age of 6 months, both
of which are prior to puberty.3,4,28,29,146–148,150
Anesthetic and Surgical
Complications
Gonadectomy is an elective procedure, and the
risk of anesthetic and surgical complications must
be considered along with the previously mentioned
long-term risks and benefits with or without gonadal
hormones. When a surgical candidate is evaluated for
gonadectomy, a veterinarian must consider age, body
weight, and existing medical conditions that may
increase the risk of anesthetic or surgical complica-
tions.150 Potential complications of soft tissue surgery
and anesthesia include hemorrhage, hypothermia,
pain, wound inflammation, delayed wound healing,
dehiscence, and death.2 9,15 0 –154 Studies28 ,15 2,15 3 based
on veterinary students performing OHE and castra-
tion have found complication rates of 20% to 30%,
but the most common complications were consid-
ered minor problems, and the rate of occurrence was
thought to be influenced by the experience of the
person performing the surgery. Complications can be
minimized through appropriate patient selection, use
of safe and efficient protocols for anesthesia, applica-
tion of minimally traumatic patient preparation and
surgical techniques, careful monitoring of patients,
and multimodal pain management including preop-
erative analgesia.150 ,15 4,15 5
JAVMA • Vol 250 • No. 10 • May 15, 2017 1163
Small Animals
Potential Areas for Future Study
Potential associations between neuter status and
other disease processes including adrenal gland dis-
ease, hypothyroidism, cognitive function, and patellar
luxation have been discussed. Adrenal gland tumors
and nodular hyperplasia have been associated with
gonadectomy in ferrets, but no associations currently
have been made between adrenal gland disease and
gonadectomy in dogs.15,2 8 Literature on the associa-
tion between neuter status and hypothyroidism has
provided mixed results, with an association indicated
in some reports156,157 and no association indicated in
other reports.4,15 8 ,159 Currently, there is insufficient
support for an association between gonadectomy and
an increased risk of hypothyroidism in dogs.15,34
The situation is similar for cognitive dysfunction.
In 1 study160 conducted to evaluate the potential ef-
fect of neuter status on cognitive function, neutered
male dogs were more likely to progress from mild to
severe cognitive impairment than were sexually in-
tact male dogs. The study160 did not have a sufficient
number of sexually intact female dogs for evaluation,
and only 6 sexually intact male dogs were available
for the final comparison. In contrast, investigators of
a study161 on the effects of testosterone on longev-
ity in humans and dogs suggested that orchiectomy
may reduce DNA damage within the brain of elderly
Beagles. However, the study161 sample size was small,
with only 4 dogs in each group. Neither neuter sta-
tus nor age at gonadectomy has been found to affect
trainability of working dogs.28
Patellar luxation is unrelated to age at gonad-
ectomy, but gonadectomized dogs may be at an in-
creased risk for patellar luxation, compared with the
risk for sexually intact dogs.4,162 A study162 conducted
to evaluate diagnostic and genetic aspects of patellar
luxation found that body weight, age, and neuter sta-
tus were associated with patellar luxation. Because
the gonadectomized dogs of that study162 were signi-
cantly older than the sexually intact dogs, the author
stated that the role (if any) of gonadectomy in the
mechanisms leading to patellar luxation could not be
deduced from the data. Age at gonadectomy of the
dogs was also unknown.162 Continued research into
these potential associations appears to be warranted.
However, analysis of the literature currently does not
justify considering these diseases when making clini-
cal decisions about if or when to spay or neuter a ca-
nine patient.
Clinical Relevance
Routine gonadectomy of companion animal dogs
is a commonly accepted procedure in the United
States. The widespread recommendation for gonad-
ectomy is based on advocating for the welfare of the
animal as well as the general canine population by
reducing the incidence of certain medical problems
and minimizing contributions to the homeless animal
population. In addition to these benefits, gonadecto-
my also has the potential to affect an individual dog’s
risk of certain diseases and disorders. Although infor-
mation about the risks associated with gonadectomy
has been reported in the past, the recommendation
for gonadectomy as a blanket policy is increasingly
controversial, with greater focus on possible ramifica-
tions for individual animals in addition to the canine
population as a whole. These risks and benefits must
be revisited as new information becomes available.
Because of the substantial national problem of home-
less animals, shelter and rescue organizations are en-
couraged to spay and neuter dogs prior to adoption
to prevent those animals from further contributing to
the population of unwanted animals.145,147 Similar to
other areas of veterinary medicine, it is the responsi-
bility of veterinarians to use their best medical judg-
ment (on the basis of each animal’s ownership, breed,
sex, and intended use) to weigh both the potential
risks and benefits when determining whether gonad-
ectomy is appropriate and, if so, the appropriate age
for the surgery.2,11,34,3 6,147,149
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... However, research over the past 2 decades has indicated that the loss of gonadal hormones can result in sequalae such as increased incidence of obesity, urinary incontinence, endocrine disorders, orthopedic conditions, cancer, and behavior and cognitive changes. [1][2][3] The mechanism underlying these problems may be the lack of negative feedback by gonadal hormones on the pituitary and hypothalamus, resulting in supraphysiologic levels of luteinizing hormone (LH). 2 The impact of gonadectomy varies by breed, size, sex, and age at neuter 4,5 supporting an individualized approach to sterilization of dogs. 6 As a result of these concerns, a growing number of veterinarians are offering hormone-preserving sterilization procedures, including vasectomy and hysterectomy. ...
... There is growing evidence linking gonadectomy with lifelong health and behavioral problems in some dogs. [1][2][3] However, little information exists on the effects of reproductive hormone therapy. This case study reported the physical and behavioral improvements following restoration of reproductive hormone concentrations in a neutered male dog. ...
Article
Full-text available
This case study reports on the use of hormone therapy to treat a dog with a range of physical and behavioral signs that began after gonadectomy. A male mixed breed dog neutered at 7 months of age presented at 1 year with health issues impacting quality of life. Reduced mobility, limping, rapid weight gain, and fear of unfamiliar people were treated over the next three years with trials of pain medication, joint supplements, thyroxine, antidepressant, and significant diet restrictions. Frequent carprofen administration and daily joint supplements reduced limping, but mobility was still poor. Weight stabilized on a strict diet but fear and anxiety responses to strangers continued to worsen. Hormone restoration therapy was initiated when the dog was almost 4 years of age. Weekly subcutaneous administration of testosterone cypionate (0.5 mg/kg) significantly reduced pain and increased muscle mass, thereby improving mobility. However, supraphysiologic concentrations of luteinizing hormone were not reduced with testosterone therapy so a gonadotropin-releasing hormone agonist was implanted. After hormone restoration, appetite was reduced, and anxiety and fear behaviors became manageable. The testosterone and gonadotropin-releasing hormone agonist treatment was easily administered, had no known side effects, and the owners were pleased with the outcome.
... The only current published study in which puberty was defined reported no differences in urination behaviour and ownerreported behaviour for 58 Labrador Retriever bitches (20). Despite the lack of evidence, many authors have implied in review papers and conference proceedings that studies using the onset of puberty have been conducted (34)(35)(36)(37)(38)(39)(40)(41). However, these appear to be based upon apparent misinterpretation of studies that investigate the impacts of neutering at different ages. ...
Article
Full-text available
There are few studies that investigate the effect of neutering bitches before or after puberty. The majority of current literature examining the impact of the timing of neutering on health and behaviour has used age rather than the onset of puberty as the key variable. The aim of this prospective cohort study was to investigate the effects of timing of neutering in relation to puberty on behaviour in female dogs reared and trained in an assistance dog programme. The study examined data for bitches neutered before or after puberty to compare scores for six behavioural factors (training and obedience, aggression, fear and anxiety, excitability, attachment and attention-seeking, and social behaviour) measured at 1 and 3 years of age. Labrador and Golden Retriever crossbreed bitches were neutered before (n = 155) or after (n = 151) puberty. Neutering before or after puberty had no impact on mean scores for the six behavioural factors at 1 or 3 years of age. When examining the change in behavioural factor scores between 1 and 3 years of age, only aggression behavioural factor scores were influenced by neutering before or after puberty. Bitches neutered after puberty were less likely to have aggression factor scores that increased between 1 and 3 years of age (OR = 0.959, 90% CI = 0.924 to 0.995, p = 0.06). However, the majority of bitches scored “0” for aggression at both time points (indicating no aggression behaviours were observed), and the number of bitches for which scores increased between 1 and 3 years of age was low (before puberty = 20, after puberty = 9). This is consistent with very mild aggressive behaviours being observed in a small number of animals and is, therefore, of questionable concern. The results suggest that, for Labrador and Golden Retriever crossbreed bitches, neutering before or after puberty has little to no effect on future behaviour. It is recommended that decisions about the timing of neutering are not informed solely by impacts on behaviour, but that they also consider evidence relating to the impacts on bitch health and well-being.
... It has been used to prevent reproduction and make males more tractable in all domestic mammal species, and even in humans (Zumpe et al., 1992). Sterilizing companion animals is considered the norm in many countries, with only 14% of dogs (Canis familiaris) remaining intact in the United States (Houlihan, 2017). Similarly the majority of domestic horses (Equus caballus) are castrated (Schumacher, 1996;Searle et al., 1999). ...
Article
Castration is commonly used to control the behavior of companion animals and livestock, yet there have been few longitudinal studies of its effects. Despite the ubiquity of this surgery in ridden horses, the effects of castration (termed gelding in horses) have rarely been examined in a reproductive population. We tested effects of gelding on maintenance and social behaviors of individuals pre- and post-gelding, and in comparison to intact control adult males (2 to >16 years old) in both harem and bachelor status, we then tested how gelding affected association with mares (i.e., maintenance of a harem group) compared to intact controls, and any effects on bachelor social associations. We further explored any effects on foaling rate to assess potential impacts on population growth rate. We conducted this study over four years (2017 to 2020) at two Herd Management Areas (HMAs) in western Utah, USA: Conger and Frisco. We conducted demographic observations year round at both HMAs to record survival and foaling rate. We additionally recorded behavioral observations at Conger HMA. In December 2017, 27 adult males from Conger (42% of adult males in the population) were gelded and returned to the range with their social groups. Due to pre-treatment observations we were able to compare stallions of known status pre- and post-treatment (harem or bachelor), as well as gelded and intact males. We had no morbidity or mortality related to the gelding surgery and all males maintained good body condition throughout the study. There was no effect of gelding on maintenance behaviors (feeding, moving, and standing). There was no effect of gelding on frequency of agonistic behavior, and a non-significant tendency for less reproductive behavior in geldings; geldings showed more affiliative and less marking behavior. Age class and/or social status were better predictors of behavior than gelding. Over time fewer geldings maintained a harem, and their harem size declined during the study. Horses that were bachelors when gelded tended to remain as bachelors, whereas intact bachelors of the same cohort mostly attained a harem. Foaling rate at Conger was reduced in the year following treatment, but then returned to pre-treatment levels. From a welfare perspective gelding is safe to use in feral horses and has minimal effects on horse behavior and social interactions in a reproductive herd. Effectiveness for population growth control would likely require a larger proportion of males in the population to be castrated for longer-term effects on foaling rate.
... The biological basis of the aggression mechanism in the case of a domestic dog is still not fully understood, but there are many indications that hormones such as testosterone, estrone, or serotonin may play a role in it [96][97][98], As indicated in the available literature, in many cases the blame for the aggressive behavior of both male and female dogs is the sex hormones found naturally in their bodies [99]. In such a case, it is often recommended to castrate or sterilize aggressive individuals in order to reduce the existing level of aggression or other behaviors perceived as negative by the owners [100,101]. ...
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Aggression as a behavior is not always desirable, often ends in abandonment and/or euthanasia. However, it is possible to prevent the occurrence of unwanted aggression in domestic dogs. Aggression is not a fully understood phenomenon. In recent years, many studies have focused on the influence of diet and physiology (including the endocrine system) on the emergence of behavioral disorders. In particular, the emphasis was put on nutritional additives such as fatty acids, amino acids, and probiotics. In addition, the possibility of using neurocognition in the observation of abnormal behavior in dogs has also been discussed, which may allow for a more detailed determination of the basis of aggressive behavior in dogs. In this review, the concepts related to aggression and its potential causes have been gathered. In addition, the possible influence of diet and hormones on aggression in dogs has been discussed, as well as the application of neurocognition in the possibility of its diagnosis
Chapter
Behavior can change as a result of medical problems or physiological changes, and behavior changes are likely to be the first signs of stress, disease, and poor welfare in any animal. If shelter operations, behavior, and/or medical staff identify behaviors that may have an underlying medical cause, they can be addressed immediately, relieving suffering and increasing the adoptability of the animal. Conversely, if medical conditions that cause or exacerbate problematic behaviors are missed, time may be wasted on training or attempted behavior modification, thus prolonging suffering and time spent in the shelter. Only by safeguarding both physical and emotional health can we improve overall quality of life for animals in our care, facilitate their placement in homes, and help prevent their return to the shelter.
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The objective of this study was to determine if overnight fasting is associated with hypoglycemia in puppies undergoing elective surgical neutering. One hundred seventy-one apparently healthy puppies between the age of 2 and 6 months presented for elective surgical neutering. Owners were instructed to withhold food from puppies after midnight the night before surgery; water was to be freely available. Blood samples were collected pre- and postoperatively to determine blood glucose, packed cell volume (PCV), and serum total protein (TP). Pre- and postoperative data were compared with a paired Wilcoxon test (paired samples). Hypoglycemia was defined as glucose <4.2 mmol/L (76 mg/dL) for pediatric puppies ≤16 weeks of age (n = 116), and <3.6 mmol/L (65 mg/dL) for juvenile puppies >16 weeks of age (n = 55). Blood glucose significantly increased after surgery from median 8.8 mmol/L (interquartile range [IQR], 1.7 mmol/L; range, 4.9-12.3 mmol/L) to a median 9.7 mmol/L (IQR, 1.8 mmol/L; range, 5.4-14.7 mmol/L; P <0.0001). Preoperative median PCV was 35% (IQR, 6.5%; range, 26-53%) and TP was 58 g/L (IQR, 6 g/L; range, 44-82 g/L). Preoperative values were significantly higher than postoperative values for PCV (median, 31%; IQR, 4%; range, 24-43%) and TP (median, 55 g/L; IQR, 7 g/L; range, 40-76 g/L; P<0.0001). No puppy developed hypoglycemia and no adverse events were observed or reported. Overnight fasting did not result in pre- or postoperative hypoglycemia in studied puppies undergoing elective neutering.
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The topic of surgical sterilization in companion animals is evolving. Although early spay and neuter has been advocated to prevent overpopulation of unwanted pets, recent research has focused on the timing of gonadectomy in relation to risk of various neoplasms, orthopedic conditions, and miscellaneous conditions. Many of these studies are breed-specific or draw from large veterinary medical databases, making it difficult to guide recommendations on the timing of sterilization across various breeds and mixed-breeds. This article attempts to synthesize the data and help guide decision making on the type and timing of sterilization procedures performed, including gonad sparing sterilization surgeries.
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Influence of neutering on canine mammary tumorigenesis has been a source of vivid discussion over the last decades. The purpose of this retrospective study was to describe the association between neuter status, tumour size and degree of malignancy in a large population of 625 female dogs with altogether 1,459 removed mammary tumours (MTs). MT-bearing dogs were predominantly intact (80.3%) and intact dogs were overrepresented in the tumour population compared to the control group of >19,000 females (p < 0.0001). Multiple MT occurred in 340 patients (54.4%) and were significantly more common in intact dogs (57.8% vs. 40.7% spayed). Neutered dogs were not only significantly more likely to have a malignant MT (p < 0.0001) but were significantly more often affected by more aggressive tumour subtypes (p < 0.0001). Positive correlation between increasing tumour size and increasingly malignant phenotype was slightly stronger in spayed (rs = 0.217; p = 0.021) compared to intact (rs = 0.179; p = 0.0003) patients. After ovariectomy, progression from benign to malignant occurs in smaller size tumours, as MT ≥ 2cm in diameter were malignant in 86.9% of the spayed patients, compared to 62.0% in intact patients (p = 0.0002). Intact bitches have a higher risk for MTs and tumour multiplicity. MTs in neutered females are more often malignant and belong to more aggressive subtypes compared to MTs in intact dogs. In neutered bitches, histologic progression from benign to malignant and further along the cancer progression continuum occurs at smaller tumour sizes. This article is protected by copyright. All rights reserved.
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Cryptorchidism is a common disorder in the canine population with some aspects still unclear. Although the bilateral condition is known to lead to fertility problems and predisposition to testicular cancer, the neoplastic risk for scrotal testis in unilateral cryptorchid dog is controversial. Therefore, the therapeutic approach to the canine unilateral cryptorchid is arbitrary so far. This study aimed to investigate precancerous testicular lesions, such as immaturity and atrophy, and compare them in scrotal and undescended testes using an in-depth diagnostic analysis based on immunophenotypic patterns. With this purpose, 26 adult male dogs of different ages and breeds, affected by unilateral or bilateral cryptorchidism were enrolled. After surgical removal, testes were examined immunohistochemically to assess their positivity for specific markers of the canine foetal/neonatal period, that is vimentin (VIM), cytokeratin (CK), desmin (DES), inhibin-α (INH), and anti-Müllerian hormone (AMH) in Sertoli cells, and placental alkaline phosphatase (PLAP) in germ cells. Except for the ubiquitous VIM, all the markers were more expressed in neoplastic gonads compared to healthy ones (P < 0.05). Similarly, testes detected with Sertoli cell-only tubules as well as with Sertoli cells hyperplasia showed higher expression than gonads without such alterations for CK, DES, AMH and PLAP, and for CK and DES, respectively (P < 0.05). The same trend was observed in undescended respect to scrotal testes even though their positivity was significant only for DES, INH and AMH (P < 0.05). Immunohistochemical positivity found in scrotal testes of unilateral cryptorchid dogs, even in absence of detectable anatomical abnormalities, was suggestive of precancerous lesions. Despite the limited sample size, this study could help to clarify the predisposition to neoplastic development in normally descended testes. These markers expression in adult life could allow identifying the early stages of the testicular carcinogenesis process besides suggesting a precautionary bilateral surgical approach in unilateral cryptorchid dogs.
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Long-acting gonadotropin-releasing hormone (GnRH) analogs, which are approved for male dogs and ferrets, have been used off-label to suppress estrus in bitches predisposed to the side effects of spaying. Health data from the past 12 years were evaluated from bitches without progestogen pretreatment that received deslorelin acetate (DA) to suppress estrus for the first time before the age of 4.5 years. The study population included 32 client-owned bitches repeatedly treated with either 4.7 mg or 9.4 mg DA implants for a period of 5.3 ± 3.4 years (range 0.5–11.3 years). Follow-up information concerning immediate side effects of DA occurring within five months after the first DA treatment (n = 23) as well as long-term side effects of sustained gonadal suppression occurring after five months up to three years (n = 2), three years up to five years (n = 2) or more than five years (n = 8) were assessed through a questionnaire. Treatment was considered successful if no major side effects requiring medical treatment occurred, which applied to 26 out of 32 (81 %) bitches. In the six remaining bitches, the following major side effects led to treatment discontinuation: persistent urinary incontinence (n = 1), reoccurring induced heat (n = 1), uterine disease (n = 3) and/or ovarian tumor (n = 3). The bitches recovered completely after surgical spaying and/or DA implant removal. Minor side effects that did not require therapy or affect animal welfare included body weight changes (n = 18), subtle behavioral changes (n = 13), induced heat (n = 12), coat changes (n = 11), pseudocyesis (n = 6), transient urinary incontinence (n = 4), and/or temporary thickening of the uterine wall with little anechogenic content (n = 2). To examine a possible causal relationship between adverse side effects and DA treatment, further studies should compare the frequency of pathologies between groups of GnRH-treated, intact and spayed bitches of similar breeds and ages. Nevertheless, DA application before the age of 4.5 years may be a means of postponing surgical spaying for several years in breeds at high risk for developing urinary incontinence. Before DA is used in bitches, owners should be fully informed regarding possible side effects.
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As community efforts to reduce the overpopulation and euthanasia of unwanted and unowned cats and dogs have increased, many veterinarians have increasingly focused their clinical efforts on the provision of spay-neuter services. Because of the wide range of geographic and demographic needs, a wide variety of spay-neuter programs have been developed to increase delivery of services to targeted populations of animals, including stationary and mobile clinics, MASH-style operations, shelter services, community cat programs, and services provided through private practitioners. In an effort to promote consistent, high-quality care across the broad range of these programs, the Association of Shelter Veterinarians convened a task force of veterinarians to develop veterinary medical care guidelines for spay-neuter programs. These guidelines consist of recommendations for general patient care and clinical procedures, preoperative care, anesthetic management, surgical procedures, postoperative care, and operations management. They were based on current principles of anesthesiology, critical care medicine, infection control, and surgical practice, as determined from published evidence and expert opinion. They represent acceptable practices that are attainable in spay-neuter programs regardless of location, facility, or type of program. The Association of Shelter Veterinarians envisions that these guidelines will be used by the profession to maintain consistent veterinary medical care in all settings where spay-neuter services are provided and to promote these services as a means of reducing sheltering and euthanasia of cats and dogs.
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German Shepherd Dogs are important in police and military work, and are a popular family pet. The debilitating joint disorders of hip dysplasia, cranial cruciate ligament tear (CCL) and elbow dysplasia can shorten a dog's useful working life and impact its role as a family member. For this study, veterinary hospital records were examined over a 14.5-year period on 1170 intact and neutered (including spaying) German Shepherd Dogs for joint disorders and cancers previously associated with neutering. The diseases were followed through 8 years of age, with the exception of mammary cancer (MC) in females that was followed through 11 years. The cancers followed, apart from mammary, were osteosarcoma, lymphoma, hemangiosarcoma and mast cell tumour. In intact males, 7% were diagnosed with one or more joint disorders, while in males neutered prior to a year of age, a significantly higher 21% were diagnosed with one or more joint disorders. In intact females, 5% were diagnosed with one or more joint disorders, while in females neutered prior to a year of age, this measure was significantly increased to 16%. The increased joint disorder incidence mostly associated with early neutering was CCL. MC was diagnosed in 4% of intact females compared with less than 1% in females neutered before 1 year. The occurrence of the other cancers followed through 8 years of age was not higher in the neutered than in the intact dogs. Urinary incontinence, not diagnosed in intact females, was diagnosed in 7% of females neutered before 1 year, a significant difference. These findings, profiling the increase in joint disorders associated with early neutering, should help guide the timing of neutering for this breed.
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The purpose of the study was to evaluate cystic endometrial hyperplasia pyometra complex (CEH-P) by clinical, pathomorphological and immunohistological findings. The 35 uterine horns of bitches aged from 2 to 11 years and different breeds were studied. Clinically polyuria, polydipsia, vomiting, anorexia and fever were seen and in some bitches distention of abdomen was noticed, Escherichia coli, Streptococcus spp., Staphylococcus spp. and Proteus spp. were isolated from uterine fluid, The uterine horns were dilated and their lumina contained moderate amounts of purulent exudate. Histopathologically, lesions were characterised by varying degrees of cystic changes of the glands and infiltration of inflammatory cells. Immunohistochemically, estrogen and progesteron receptor positive areas were determined.
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Prepubertal gonadectomy, or early-age neutering, has become common in many humane organizations as a method of population control. The concept of prepubertal gonadectomy has remained controversial among veterinarians despite the lack of scientific data to support current recommendations regarding the ideal age at which dogs and cats should be neutered. Studies suggest that gonadectomy is safe in dogs and cats as young as 6 weeks of age; however, many veterinarians are reluctant to anesthetize and perform surgery on pediatric patients. Part I discusses the history of prepubertal gonadectomy, physiologic differences between pediatric and adult animals, and general anesthetic and surgical considerations. Part II will address surgical procedures as well as the safety of performing prepubertal gonadectomy.
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Introduction: The aim of the study was to investigate a diagnostic protocol for patellar luxation (PL) in respect to its usability as a screening method in the framework of breeding programs. Further, the influence of breed, age, body mass, gender and neutering on the prevalence of PL has been investigated. Methods: In a period of 8 years (1996-2004) 432 small and miniature-breed dogs have been examined for patellar luxation. In order to achieve the diagnostic efficiency required for genetic screenings performed in the framework of breeding programs, this examination was based on the concept of a standardized examination protocol that included clinically examination with inspection as well as palpation. The diagnostic criteria were lameness, palpation and evaluation of patellar tracking in standing and recumbent position of the dog with special focus on the presence of any patellofemoral instability. A further diagnostic criterion was the deviation of the tibial tuberosity and any perceivable crepitation of the knee joint during all manipulations performed. The findings of patellar luxation were valuated according to PUTNAM's (1968) graduation. X-rays have not been performed. To find out whether the investigated diagnostic criteria fulfil the demands on consistency and validity needed for screening, diagnostic rank correlation coefficients between the single diagnostic criteria and the final PL-finding have been calculated. The influence of breed, age, body mass, gender and neutering on the occurrence of PL was investigated by calculating odds ratios using a multifactorial logistic regression model. The significance testing of the resulting odds ratios was performed by calculating the corresponding 95 % confidence intervall. Results: In 61.6 % of the examined dogs we found patellar luxation, but only in 15.5 % (right knee) and 12.8 % (left knee) a permanent lameness could be observed; in 3.5 % (right kee) and 4.6 % (left knee) there was an intermittent lameness. Therefore nearly 40 % of the animals with patellar luxation were clinically normal and would not have been detected as carriers of patellar luxation without screening diagnostic. The investigated diagnostic criteria showed significant correlation among each other and with the final PL-finding and therefore proved to be consistent and meaningful with regard to PL- investigation. The parameters "luxation in standing" and "luxation in recumbent position" showed the highest rank-correlation to the final findings. Thus it appears that, in general, this examination protocol is suitable for PL-screenings. The investigation of the influence of the parameters "body mass", "age", "gender" and "neutering" on the occurrence of PL showed that except "gender" all attributes are associated with occurrence of PL. An increase in body mass of 1 kg decreases the odds of suffering from PL to the 0.8fold (p < 0.05), an increase of age of one year increases the odds of suffering from PL to the 1.1fold (p = 0.051). Neutered dogs showed a 3.10fold odds for suffering from PL (p < 0.05). To detect breed predispositions for patellar luxation odds ratios were calculated for each breed that was represented in the study by more than 10 animals, including Jack Russell Terrier, Mops, Papillon, Pekingese, Shih Tzu, Tibet Terrier, West Highland White Terrier, Poodle, Yorkshire Terrier, Malteser and Chihuahua. 2 breeds showed a significantly different outcome with regard to increase of suffering from PL. The Jack Russell Terrier had an odds ratio of 0.31 with corresponding 95 % confidence intervals 0.14 -0.67 and therefore showed a reduced chance of PL compared with all other breeds. On the other hand the Poodles (including the miniature- and toy-variants) with an odds ratio of 5.62 with corresponding 95 % confidence intervals 1.93-16.41 showed a higher chance of PL compared with all other breeds. This result gives some evidence on a genetic background of PL. Nevertheless the genetic basis of PL should be investigated more accurately by family analyses and heritability studies. Conclusions: Referring to the consistency and validity of the diagnostic criteria the diagnostic protocol used in this study seems to be suitable as screening method for PL. As 2 of the investigated breeds showed a significantly higher or lower chance for suffering from PL a genetic background of PL can be postulated. Based on the results of this study it would be highly recommended for breeding associations to introduce screening programs for patellar luxation in small and miniature breed dogs as described in this study in combination with a redefinition of breeding goals aimed at the extreme miniaturization of the affected dog breeds.
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Focusing on cancer in dogs and cats, this extensively updated 4th edition provides comprehensive coverage of the latest advances in clinical oncology, including chemotherapy, surgical oncology, and diagnostic techniques. Ideal for students, practitioners, and those involved in academic research, this book's full-color images and user-friendly format provide quick and easy access to today's most important information on cancer in the small animal patient. Full-color format throughout and full-color illustrations make information more accessible and provide accurate representations of clinical appearance. Chapters are clustered into four major sections: The Biology and Pathogenesis of Cancer, Diagnostic Procedures for the Cancer Patient, Therapeutic Modalities for the Cancer Patient, and Specific Malignancies in the Small Animal Patient. The consistent format includes incidence and risk factors, pathology, natural behavior of tumors, history and clinical signs, diagnostic techniques and workup, treatment options, and prognosis for specific malignancies in the small animal cancer patient. Features cutting edge information on the complications of cancer, pain management, and the latest treatment modalities. The latest information on the etiology of cancer, including genetic, chemical, physical, and hormonal factors, as well as cancer-causing viruses. Coverage of molecular-targeted therapy of cancer, plus new and emerging therapeutic techniques. New information on molecular diagnostic procedures for the cancer patient. The latest diagnostic imaging techniques in clinical oncology. Discussions of compassion and supportive care, from chronic pain management and nutrition to end-of-life issues and grief support.