Spay or Not and At What Age?
You'll hear many things about whether or not and what age to alter a dog. You need to do your research before you decide what is appropriate for you, your dog and your situation. This is an especially important consideration for service dogs since certification depends the behavioral and physical abilities of the dog. Spaying and neutering too early results in health and behavioral issues in many dogs.
Why & When Is Altering Done?
Spaying and neutering is typically done as a prevention for population explosion/unwanted dogs and to prevent health issues such as cancers (experts are now question the validity of this belief.). A common practice in some regions has been to alter the puppies as young as 8 weeks before they go to their new homes (This is seen most commonly in dogs from shelters and rescue organizations and some breeders) Recent long-term studies have shown juvenile altering is not a good idea.
What is Done to the Dogs?
Spaying and Neutering a dog removes the sex organs and hormones associated with them. In females the uterus is removed (as in human hysterectomy) and the ovaries. In neutering (also known as castration) the male's testicles are removed.
Long term Effects of Spaying Too Early
Dogs spayed or neutered as juveniles (less than 6 mos old) show many undesirable long-term effects. What occurs is that the hormones normally emitted by the sex glands are not present and this affects both the temperament and physical development of the dogs in question. In females, fearfulness, overly long leg bones, low bone density issues, hip dysplasia, ACL tears and increased risks of cancer have been identified. In males, all of the above except fearful nature is replaced by aggression.
Two long-term studies of a large number of dogs show behavioral and physical effects are a real possibility.
*In 1998 and 1999, 1444 Golden Retrievers by the Golden Retriever Club of America
*German Shepherd Dogs
Overall Summary of Studies done on animals altered at a juvenile age. http://www.caninesports.com/SpayNeuter.html
What Age Is ideal?
If you are going to spay/neuter you service dog, a minimum age is just at the time the dog reaches physical maturity. At least 1 year for small breeds, 18 mos for middle size dogs and about 2 years for giant breeds. This way, physical development (especially the bone plates which is among the last to mature) has been completed. The ideal age may also be affected by sex. (Im HH, Yeon SC, Houpt KA, et al. Effects of ovariohysterectomy on reactivity in German shepherd dogs. Vet J 2006;172(1):154-159.)
Guide Dog programs typically spay females after their first heat and males at about 8 months of age. Could this partly explain the high failure rate of dogs due to behavioural issues (some as high as 50%)?
Is Spaying/Neutering Necessary?
Do you need to alter your animal at all? That depends on the laws of the your region, the breeder, the program you belong to and the individual dog in question.
Does altering males actually decrease or prevent aggression issues? Studies show that if the altering is done at the time of puberty, it decreases the hormonal levels and usually results in calmer behaviour such as less wandering. If the altering is done after puberty, there may be no behavioral improvement.
Here is a link to a summary of studies on spaying and neutering risks and benefits of dogs at all ages.
If your situation allows you to choose not to spay or neuter you dog, be a responsible owner and do not allow your animal to reproduce, unless you are knowledgeable and experienced in the area of breeding.
One way to do this without spaying or neutering is ask your vet to do a vasectomy on your male dog or perform a tubal ligation in your female dog. This stops all possibility of reproducing without altering the natural hormone levels in the dog. Do be warned, though, these operations, while actually easier to perform are not common and the vets may not want to do them. You may need to educate your vet or find one who is willing to do it. Only you can decide if the benefits are worth the extra effort.
Of course the common sense method of preventing your female from breeding is to protect her from male dogs (with solid fences etc) when in heat and keep your male dog with you at all times.