Early Spay-Neuter Considerations
for the Canine Athlete
One Veterinarian's Opinion
© 2005 Chris Zink DVM, PhD, DACVP
Those of us with responsibility for the health of canine athletes need to
continually read and evaluate new scientific studies to
ensure that we are taking the most appropriate care of our performance dogs.
This article provides evidence through a number of
recent studies to suggest that veterinarians and owners working with canine
athletes should revisit the standard protocol in which al
dogs that are not intended for breeding are spayed and neutered at or before 6
months of age.
Orthopedic Considerations
A study by Salmeri et al in 1991 found that bitches spayed at 7 weeks grew
significantly taller than those spayed at 7 months, who were
taller than those not spayed (or presumably spayed after the growth plates had
closed).(1) A study of 1444 Golden Retrievers performed in
1998 and 1999 also found bitches and dogs spayed and neutered at less than a
year of age were significantly taller than those spayed or
neutered at more than a year of age.(2) The sex hormones, by communicating with
a number of other growth-related hormones, promote
the closure of the growth plates at puberty (3), so the bones of dogs or bitches
neutered or spayed before puberty continue to grow. Dogs
that have been spayed or neutered well before puberty can frequently be
identified by their longer limbs, lighter bone structure, narrow
chests and narrow skulls. This abnormal growth frequently results in significant
alterations in body proportions and particularly the
lengths (and therefore weights) of certain bones relative to others. For example,
if the femur has achieved its genetically determined
normal length at 8 months when a dog gets spayed or neutered, but the tibia,
which normally stops growing at 12 to 14 months of age
continues to grow, then an abnormal angle may develop at the stifle. In
addition, with the extra growth, the lower leg below the stifle
likely becomes heavier (because it is longer), and may cause increased stresses
on the cranial cruciate ligament. In addition, sex
hormones are critical for achieving peak bone density.(4) These structural and
physiological alterations may be the reason why at
least one recent study showed that spayed and neutered dogs had a higher
incidence of CCL rupture.(5) Another recent study showed that
dogs spayed or neutered before 5 1/2 months had a significantly higher incidence
of hip dysplasia than those spayed or neutered after
5 1/2 months of age, although it should be noted that in this study there were
no standard criteria for the diagnosis of hip
dysplasia.(6) Nonetheless, breeders of purebred dogs should be cognizant of
these studies and should consider whether or not pups
they bred were spayed or neutered when considering breeding decisions.
Cancer Considerations
A retrospective study of cardiac tumors in dogs showed that there was a 5 times
greater risk of hemangiosarcoma, one of the three most
common cancers in dogs, in spayed bitches than intact bitches and a 2.4 times
greater risk of hemangiosarcoma in neutered dogs as
compared to intact males.(7) A study of 3218 dogs demonstrated that dogs that
were neutered before a year of age had a significantly
increased chance of developing bone cancer.(8) A separate study showed that
neutered dogs had a two-fold higher risk of developing
bone cancer.(9) Despite the common belief that neutering dogs helps prevent
prostate cancer, at least one study suggests that neutering
provides no benefit.(10) There certainly is evidence of a slightly increased
risk of mammary cancer in female dogs after one heat cycle,
and for increased risk with each subsequent heat. While about 30 % of mammary
cancers are malignant, as in humans, when caught and
surgically removed early the prognosis is very good.(12) Luckily, canine
athletes are handled frequently and generally receive prompt
veterinary care.
Behavioral Considerations
The study that identified a higher incidence of cranial cruciate ligament
rupture in spayed or neutered dogs also identified an
increased incidence of sexual behaviors in males and females that were neutered
early.(5) Further, the study that identified a higher
incidence of hip dysplasia in dogs neutered or spayed before 5 1/2 months also
showed that early age gonadectomy was associated with an
increased incidence of noise phobias and undesirable sexual behaviors.(6) A
recent report of the American Kennel Club Canine
Health Foundation reported significantly more behavioral problems in spayed and
neutered bitches and dogs. The most commonly observed
behavioral problem in spayed females was fearful behavior and the most common
problem in males was aggression.(12)
Other Health Considerations
A number of studies have shown that there is an increase in the incidence of
female urinary incontinence in dogs spayed early (13),
although this finding has not been universal. Certainly there is evidence that
ovarian hormones are critical for maintenance of
genital tissue structure and contractility.(14, 15) Neutering also has been
associated with an increased likelihood of urethral
sphincter incontinence in males.(16) This problem is an inconvenience, and not
usually life-threatening, but nonetheless one
that requires the dog to be medicated for life. A health survey of several
thousand Golden Retrievers showed that spayed or neutered
dogs were more likely to develop hypothyroidism.(2) This study is consistent
with the results of another study in which neutering and
spaying was determined to be the most significant gender-associated
risk factor for development of hypothyroidism.(17) Infectious diseases were more
common in dogs that were spayed or neutered at 24
weeks or less as opposed to those undergoing gonadectomy at more than 24 weeks.(18)
Finally, the AKC-CHF report demonstrated a higher
incidence of adverse reactions to vaccines in neutered dogs as compared to
intact.(12)
I have gathered these studies to show that our practice of routinely spaying or
neutering every dog at or before the age of 6 months is
not a black-and-white issue. Clearly more studies need to be done to evaluate
the effects of prepubertal spaying and neutering,
particularly in canine athletes.
Currently, I have significant concerns with spaying or neutering canine athletes
before puberty. But of course, there is the pet
overpopulation problem. How can we prevent the production of unwanted dogs while
still leaving the gonads to produce the hormones that are
so important to canine growth and development? One answer would be to perform
vasectomies in males and tubal ligation in females, to be
followed after maturity by ovariohysterectomy in females to prevent mammary
cancer and pyometra. One possible disadvantage is that
vasectomy does not prevent some unwanted behaviors associated with males such as
marking and humping. On the other hand, females and
neutered males frequently participate in these behaviors too. Really, training
is the best solution for these issues. Another possible
disadvantage is finding a veterinarian who is experienced in performing these
procedures. Nonetheless, some do, and if the
procedures were in greater demand, more veterinarians would learn them.
I believe it is important that we assess each situation individually. For canine
athletes, I currently recommend that dogs and bitches be
spayed or neutered after 14 months of age.
References:
Salmeri KR, Bloomberg MS, Scruggs SL, Shille V.. Gonadectomy in immature dogs:
effects on skeletal, physical, and behavioral
development. JAVMA 1991;198:1193-1203 http://www.grca.org/healthsurvey.pdf
Grumbach MM. Estrogen, bone, growth and sex: a sea change in conventional wisdom.
J Pediatr Endocrinol Metab. 2000;13 Suppl
6:1439-55.
Gilsanz V, Roe TF, Gibbens DT, Schulz EE, Carlson ME, Gonzalez O, Boechat MI.
Effect of sex steroids on peak bone density of growing
rabbits. Am J Physiol. 1988 Oct;255(4 Pt 1):E416-21. Slauterbeck JR,
Pankratz K, Xu KT, Bozeman SC, Hardy DM. Canine
ovariohysterectomy and orchiectomy increases the prevalence of ACL injury. Clin
Orthop Relat Res. 2004 Dec;(429):301-5.
Spain CV, Scarlett JM, Houpt KA. Long-term risks and benefits of early-age
gonadectomy in dogs. JAVMA 2004;224:380-387.
Ware WA, Hopper DL. Cardiac tumors in dogs: 1982-1995. J Vet Intern Med 1999
Mar-Apr;13(2):95-103
Cooley DM, Beranek BC, Schlittler DL, Glickman NW, Glickman LT, Waters D, Cancer
Epidemiol Biomarkers Prev. 2002 Nov;11(11):1434-40
Ru G, Terracini B, Glickman LT. Host related risk factors for canine
osteosarcoma. Vet J. 1998 Jul;156(1):31-9. Obradovich J, Walshaw R,
Goullaud E. The influence of castration on
the development of prostatic carcinoma in the dog. 43 cases
(1978-1985). J Vet Intern Med 1987 Oct-Dec;1(4):183-7 http://www.akcchf.org/pdfs/whitepapers/Biennial_National_Parent_Club_C
anine_Health_Conference.pdf Meuten DJ. Tumors in Domestic Animals. 4th Edn.
Iowa State Press,
Blackwell Publishing Company, Ames, Iowa, p. 575 Stocklin-Gautschi NM,
Hassig M, Reichler IM, Hubler M, Arnold S. The
relationship of urinary incontinence to early spaying in bitches. J. Reprod.
Fertil. Suppl. 57:233-6, 2001
Pessina MA, Hoyt RF Jr, Goldstein I, Traish AM. Differential effects of
estradiol, progesterone, and testosterone on vaginal structural
integrity. Endocrinology. 2006 Jan;147(1):61-9. Kim NN, Min K, Pessina MA,
Munarriz R, Goldstein I, Traish AM.
Effects of ovariectomy and steroid hormones on vaginal smooth muscle
contractility. Int J Impot Res. 2004 Feb;16(1):43-50.
Aaron A, Eggleton K, Power C, Holt PE. Urethral sphincter mechanism incompetence
in male dogs: a retrospective analysis of 54 cases. Vet
Rec. 139:542-6, 1996
Panciera DL. Hypothyroidism in dogs: 66 cases (1987-1992). J. Am. Vet. Med.
Assoc., 204:761-7 1994
Howe LM, Slater MR, Boothe HW, Hobson HP, Holcom JL, Spann AC. Long-term outcome
of gonadectomy performed at an early age or
traditional age in dogs. J Am Vet Med Assoc. 2001 Jan 15;218(2):217-21.
This article is available for download in Adobe Acrobat PDF format Early Spay
Considerations (pdf).
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