Early Spay-Neuter Considerations for the Canine Athlete

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Early Spay-Neuter Considerations for the Canine Athlete
By Chris Zink DVM, Ph.D.
www.caninesports.com

There are a number of studies that suggest that those of us with
canine athletes should be carefully considering our current recommendations
to spay or neuter all dogs at 6 months of age or earlier. A study by
Salmeri et al in 1991 (Salmeri et al JAVMA 1991;198:1193-1203) found
that bitches spayed at 7 weeks were significantly taller than those
spayed at 7 months, who were significantly taller than those not
spayed (or presumably spayed after the growth plates had closed). The sex
hormones close the growth plates, so the bones of dogs or bitches
neutered or spayed before puberty continue to grow. This growth
frequently results in a dog that does not have the same body
proportions as he/she was genetically meant to. For example, if the
femur is 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
becomes heavier (because it is longer), causing increased stresses on the
cranial cruciate ligament. This is confirmed by a recent study showing
that spayed and neutered dogs have a higher incidence of CCL rupture
(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).

In addition, a study in 2004 in JAVMA (Spain et al. JAVMA
2004;224:380-387) showed that dogs spayed or neutered before 5 1/2
months had a significantly higher incidence of hip dysplasia than dogs
spayed or neutered after 5 1/2 months of age. If I were a breeder, I
would be very concerned about this, because it would mean that I might
be making incorrect breeding decisions if I were considering the hip
status of pups I sold that were spayed or neutered early.
Interestingly, this same author also identified an increased incidence
of sexual behaviors in males and females that were neutered early.

A number of studies, including the one by Spain referenced above, have
shown that there is an increase in the incidence of female urinary
incontinence in dogs spayed early. This problem is an inconvenience,
and not usually life-threatening, but nonetheless one that requires
the dog to be medicated for life.

Yes, there is the concern that there is an increased risk of mammary
cancer if a dog has a heat cycle. But it is my observation that fewer
canine athletes develop mammary cancer as compared to the number that
damage their cranial cruciate ligaments. In addition, only about 50 %
of mammary cancers are malignant, and those that are malignant don't
metastasize very often, particularly in these days when there is early
identification and removal of lumps found on our dogs.

In addition, when considering cancer, there is another study of 3218
dogs that showed that dogs that were neutered before a year of age had
a significantly increased chance of developing bone cancer (Cooley DM,
Beranek BC, Schlittler DL, Glickman NW, Glickman LT, Waters D, Cancer
Epidemiol Biomarkers Prev. 2002 Nov;11(11):1434-40), a cancer that is
much more life-threatening than mammary cancer, and which affects both
genders.

Finally, in another study, unneutered males were significantly less
likely than neutered males to suffer cognitive impairment when they
were older (Hart BL. J Am Vet Med Assoc. 2001 Jul 1;219(1):51-6).
Females were not evaluated in that study.

For these reasons, I have significant concerns with spaying or
neutering dogs before puberty, particularly for the canine athlete.
And frankly, if something is more healthy for the canine athlete, would we
not also want that for pet dogs as well? I think it is important,
therefore, that we assess each situation individually. If a pet dog is
going to live with an intelligent, well-informed family that
understands the problem of pet overpopulation and can be trusted to
keep their dogs under their control at all times and to not breed
them, I do not recommend spaying or neutering before 14 months of age.

Chris Zink

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The relationship of urinary incontinence to early spaying in bitches.
J Reprod Fertil Suppl 57:233-6 2001
Stocklin-Gautschi NM, Hassig M, Reichler IM, Hubler M, Arnold S
It is still controversial whether a bitch should be spayed before or after the first oestrus. It would be desirable to spay bitches at an age that would minimize the side effects of neutering. With regard to the risk of mammary tumours, early spaying must be recommended because the incidence of tumours is reduced considerably. The aim of the present study was to determine whether early spaying also reduces the risk of urinary incontinence. The owners of 206 bitches that had been spayed before their first oestrus and for at least 3 years were questioned on the occurrence of urinary incontinence as a result of spaying. At the time of the enquiry the average age of the bitches was 6.5 years, and the average age at the time of surgery was 7.1 months. Urinary incontinence after spaying occurred in 9.7% of bitches. This incidence is approximately half that of spaying after the first oestrus. Urinary incontinence affected 12.5% of bitches that were of a large body weight (> 20 kg body weight) and 5.1% of bitches that were of a small body weight (< 20 kg body weight). The surgical procedure (ovariectomy versus ovariohysterectomy) had no influence on the incidence, or on the period between spaying and the occurrence of urinary incontinence. Urinary incontinence occurred on average at 2 years and 10 months after surgery and occurred each day, while the animals were awake or during sleep. However, compared with late spaying the clinical signs of urinary incontinence were more distinct after early spaying.

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1: J Am Vet Med Assoc. 2004 Feb 1;224(3):380-7. Links

Comment in:
J Am Vet Med Assoc. 2004 Apr 1;224(7):1070; author reply 1070-1.
Long-term risks and benefits of early-age gonadectomy in dogs.
a.. Spain CV,
b.. Scarlett JM,
c.. Houpt KA.
Department of Population Medicine and Diagnostic Science, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA.

OBJECTIVE: To evaluate the long-term risks and benefits of early-age gonadectomy, compared with traditional-age gonadectomy, among dogs adopted from a large animal shelter. DESIGN: Retrospective cohort study. ANIMALS: 1,842 dogs. PROCEDURE: Dogs underwent gonadectomy and were adopted from an animal shelter before 1 year of age; follow-up was available for as long as 11 years after surgery. Adopters completed a questionnaire about their dogs' behavior and medical history. When possible, the dogs' veterinary records were reviewed. Associations between the occurrence of 56 medical and behavioral conditions and dogs' age at gonadectomy were evaluated. RESULTS: Among female dogs, early-age gonadectomy was associated with increased rate of cystitis and decreasing age at gonadectomy was associated with increased rate of urinary incontinence. Among male and female dogs with early-age gonadectomy, hip dysplasia, noise phobias, and sexual behaviors were increased, whereas obesity, separation anxiety, escaping behaviors, inappropriate elimination when frightened, and relinquishment for any reason were decreased. CONCLUSIONS AND CLINICAL RELEVANCE: Because early-age gonadectomy appears to offer more benefits than risks for male dogs, animal shelters can safely gonadectomize male dogs at a young age and veterinary practitioners should consider recommending routine gonadectomy for client-owned male dogs before the traditional age of 6 to 8 months. For female dogs, however, increased urinary incontinence suggests that delaying gonadectomy until at least 3 months of age may be beneficial.

1: J Small Anim Pract. 1998 Dec;39(12):559-66. Links

Acquired urinary incontinence in bitches: its incidence and relationship to neutering practices.
a.. Thrusfield MV,
b.. Holt PE,
c.. Muirhead RH.
Department of Veterinary Clinical Studies, University of Edinburgh, Royal (Dick) School of Veterinary Studies, Easter Bush Veterinary Centre, Roslin, Midlothian.

A five-year cohort study was conducted on bitches chosen by a sample of 233 randomly selected practising veterinary surgeons in the UK, to estimate the incidence of acquired urinary incontinence (AUI) in neutered and entire animals, and to investigate possible risk factors associated with neutering practices. Information was collected using questionnaires, and data on 809 bitches, of which 22 developed AUI, were obtained. The estimated incidence rates in neutered and entire animals were 0.0174 and 0.0022 per animal-year, respectively (95 per cent confidence intervals: 0.0110, 0.0275 and 0.0009, 0.0058, respectively). The relative risk, neutered vs entire, was 7.8 (95 per cent confidence interval: 2.6, 31.5). The attributable proportion(exposed) and population attributable proportion were 87.1 per cent and 63.1 per cent (95 per cent confidence intervals: 61.9 per cent, 95.6 per cent, and 28.3 percent, 88.5 per cent, respectively). An increased risk, significant at the conventional 5 per cent level, was not demonstrated in animals neutered before, vs after, first heat (relative risk: 3.9, 95 per cent confidence interval: 0.8, 10.4), although the result was significant at the 10 per cent level. Removal of the cervix was not shown to be a risk factor in neutered dogs.

1: Urol Res. 1998;26(6):417-22. Links

Influence of ovariectomy on the canine striated external urethral sphincter (M. urethralis): a stereological analysis of slow and fast twitch fibres.
a.. Augsburger HR,
b.. Cruz-Orive LM.
Institute of Veterinary Anatomy, University of Zurich, Switzerland.

Slow and fast twitch fibres were stereologically analysed in the morphologically defined and most strongly developed ventral and ventrolateral region of the external urethral sphincter (M. urethralis) using five sexually intact anestrous and five ovariectomized nulliparous beagles. The estimated mean total cross-sectional area of the investigated part of the muscle consisted of 4.2 mm2 (15.1%) type I fibre, 10.0 mm2 (32.1%) type II fibre, and 16.3 mm2 (52.8%) connective tissue in the control group. The corresponding absolute mean value of type I fibres (3.7 mm2/13.5%) was statistically lower in ovariectomized animals. No significant difference between groups was observed in the relative number of transverse profiles of type I and II fibres; type I fibres comprised 23.8% and type II 76.2% of all muscle fibres in the sexually intact group, but 21.8% and 78.2% in the ovariectomy group, respectively. The ovariectomized dogs exhibited a statistically significant lower type I and II fibre number and a concomitant slightly larger mean single profile area (diameter) of fibre type II compared with the control animals. The significantly reduced number and decreased total cross-sectional area of the fatigue-resistant type I fibres in ovariectomized dogs suggest a predominant weakening of the fibre type I portion of the M. urethralis as consequence of ovariectomy. The effect could be mediated by sex hormonal factors and may contribute to the development of postspaying urinary incontinence in female dogs.