there is not cut and dry answer as a matter of fact the US is one of the few country in the world that nueters males as routine for population control. There is evidence on the health side that still sapying a female overall is healthier than not but that is very close in Males unfortunatle the evidence points to leaving them intacted as healthier for them.
Ok on the the hieght issue early sapying that is juvenile spay at the age of 8-16 weeks delays the closure of the growth plates. as it is assumed the sex hormones play a part in the signaling to close. That means on average the early spay/nuetered dog is 1/4 taller than the same intacted dog. This increase in hight gets smaller as the age the dog is spayed become older. Not a lot but it can be significant as you see mean the difference in being able to compete or not there are also some ortho issue that may be exaserbated by this extra hight hip displasia. Acl injuries etc. Also the delay in closure of the growth plate may have and effect on things like angular limb deformities and such if the age of the dog at spaying occurs at the time of or after some growth plates close but not all. this could cause a delay in closing of some of the open plate creating an uneven unatural growth rate between bone pairs.
Also early spay and nueter effect the appearance of the dog they tend to look more juvenile and less like adults,.
Gonadectomy in immature dogs: effects on skeletal, physical, and behavioral development
see the following articles
Early Spay-Neuter Considerations for the Canine Athlete
Growth plate closure was delayed (group I vs group III; P less than 0.000001; group II vs group III, P less than 0.000001) in all neutered dogs, as compared with sexually intact dogs. Growth plate closure was delayed longer (group I vs group II, P less than 0.000045) in dogs neutered at 7 weeks old, compared with dogs neutered at 7 months old. The rate of growth was unaffected by gonadectomy, but the extended growth period resulted in greater final radial/ulnar length in all male dogs and bitches neutered at 7 weeks.
One Veterinarian's Opinion
Keep in mind in this article early spay/nueter is defined as before sexual maturity ie 14-18 months for the average dog.
Rebutal to Chris Zink
Couple things obvious the person that Chris Zink is female, that this was specifical address to dogs destine to become or participate in atheletic endevor not all dogs and this author clear did not understand Ms zink use of early spay and nueter to mean before sexual maturity vs the more common definition of before normal six month spaying i.e. juvinile spaying at 8-16 weeks alot of the argument become mute when this is understood.
Long-Term Health Risks and Benefits Associated with Spay / Neuter in Dogs
On balance, it appears that no compelling case can be made for neutering most male dogs, especiallyimmature male dogs, in order to prevent future health problems. The number of health problems associated with neutering may exceed the associated health benefits in most cases.
On the positive side, neutering male dogs
eliminates the small risk (probably <1%) of dying from testicular cancer
reduces the risk of non-cancerous prostate disorders
reduces the risk of perianal fistulas
may possibly reduce the risk of diabetes (data inconclusive)
On the negative side, neutering male dogs
if done before 1 year of age, significantly increases the risk of osteosarcoma (bone cancer); this is a common cancer in medium/large and larger breeds with a poor prognosis.
increases the risk of cardiac hemangiosarcoma by a factor of 1.6
triples the risk of hypothyroidism
increases the risk of progressive geriatric cognitive impairment
triples the risk of obesity, a common health problem in dogs with many associated health problems
quadruples the small risk (<0.6%) of prostate cancer
doubles the small risk (<1%) of urinary tract cancers
increases the risk of orthopedic disorders
increases the risk of adverse reactions to vaccinations
Also population control the basic premise of nuetering is suspect as well since males can not have puppies population control is more effective when the female population is spayed rather than nuetering males.
Benefits of Castration in Male Dogs
Even though castration eliminates male dog’s reproductive capacity, the overall effect on pet overpopulation is minimal.
Contrary to popular belief, the study found little evidence that castration was an effective treatment for aggressive behavior in male dogs, and may exacerbate other behavioral problems. Further research will be needed to clarify the relationship between age of spaying/neutering and these apparent effects on behavior
The bigest Scientifically valid reasons to nuetering seem to be reduced incidence of urine marking and less desire to roam. Roaming is best cure with containment ie fence and Urine Marking is just as effectively treated by nuetering an adult as nuetering a puppy. There is not much of a scientific basis for nuetering male dogs. Like I said this is one of very few countries that do it routinely.