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