This is an incredibly controversial subject. Different vets you talk to will give you different recommendations and posts on this frequently devolve into massive arguments. The latest research shows that waiting until at least 1 year of age, preferably 2 years will reduce the risks of several health issues associated with Spay or Neutering. There are, however, many reasons a dog may get spayed or neutered before this age, from behavioral issues to the difficulties around preventing accidental puppies.
Recent Research: https://www.ucdavis.edu/news/early-neutering-poses-health-risks-german-shepherd-dogs-study-finds/
Dr. Karen Becker has a thorough and informative video on the subject: https://www.youtube.com/watch?v=enPCZA1WFKY
With a corresponding article: http://healthypets.mercola.com/sites/healthypets/archive/2013/09/30/neutering-health-risks.aspx
Some additional “light reading”:
- Spay, Neuter And Joint Disease: http://www.dogsnaturallymagazine.com/spay-neuter-and-joint-disease/
- Long term effects, which clearly outlines the pros/cons: http://www.naiaonline.org/pdfs/LongTermHealthEffectsOfSpayNeuterInDogs.pdf
- Considerations, including increase in fears, sound sensitivity, and aggression: http://www.caninesports.com/uploads/1/5/3/1/15319800/earlyspayconsiderations.pdf
- Concerning aggression and fearful dogs: http://www.doglistener.co.uk/neutering/spaying_neutering.shtml
- Behavior and physical affects, which shows the correlation between neutering and increased aggression: http://www.atftc.com/health/SNBehaviorBoneDataSnapShot.pdf
- Increase in bone cancer: http://cebp.aacrjournals.org/content/11/11/1434.full
- Article: https://www.avma.org/News/JAVMANews/Pages/100301g.aspx
- Neutering Dogs: Effects on Joint Disorders and Cancers in Golden Retrievers: http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0055937
- Your Dog Needs To Be Spayed Or Neutered – Right? http://www.dogsnaturallymagazine.com/your-dog-needs-to-be-spayed-or-neutered-right/
- Effects of ovariohysterectomy on reactivity in German Shepherd dogs: http://www.sciencedirect.com/science/article/pii/S109002330500064X
- Goldens more at risk than Labs: http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0102241
- The easy to understand version: http://www.veterinarypracticenews.com/Sterilization-Effects-Worse-for-Golden-Retrievers-Than-Labs/
- Evaluation of the risk and age of onset of cancer and behavioral disorders in gonadectomized Vizslas http://www.ncbi.nlm.nih.gov/pubmed/24432963
- The Vizsla study involved 2,505 dogs, and reported these results:
- Dogs neutered or spayed at any age were at significantly increased risk for developing mast cell cancer, lymphoma, all other cancers, all cancers combined, and fear of storms, compared with intact dogs.
- Females spayed at 12 months or younger, and both genders neutered or spayed at over 12 months had significantly increased odds of developing hemangiosarcoma, compared with intact dogs.
- Dogs of both genders neutered or spayed at 6 months or younger had significantly increased odds of developing a behavioral disorder, including separation anxiety, noise phobia, timidity, excitability, submissive urination, aggression, hyperactivity, and/or fear biting. When it came to thunderstorm phobia, all neutered or spayed Vizslas were at greater risk than intact Vizslas, regardless of age at neutering.
- The younger the age at neutering, the earlier the age at diagnosis with mast cell cancer, cancers other than mast cell, hemangiosarcoma, lymphoma, all cancers combined, a behavioral disorder, or fear of storms.
- Compared to intact dogs, neutered and spayed dogs had a 3.5 times higher risk of developing mast cell cancer, regardless of what age they were neutered.
- Spayed females had nine times higher incidence of hemangiosarcoma compared to intact females, regardless of when spaying was performed, however, no difference in incidence of this type of cancer was found for neutered vs. intact males.
- Neutered and spayed dogs had 4.3 times higher incidence of lymphoma (lymphosarcoma), regardless of age at time of neutering.
- Neutered and spayed dogs had five times higher incidence of other types of cancer, regardless of age of neutering.
- Spayed females had 6.5 times higher incidence of all cancers combined compared to intact females, and neutered males had 3.6 times higher incidence than intact males.
- Neutering: This Common Procedure Can Boost Cancer and Joint Problems As Much As Five-Fold, specifically Golden Retrievers: http://healthypets.mercola.com/sites/healthypets/archive/2014/11/05/neutered-golden-retrievers.aspx
- Sterilization Effects Worse for Golden Retrievers Than Labs, time of alteration on role in the onset of joint disorders and cancer: http://www.veterinarypracticenews.com/Sterilization-Effects-Worse-for-Golden-Retrievers-Than-Labs/
- OSS (ovary sparing spay): http://healthypets.mercola.com/sites/healthypets/archive/2013/09/23/modified-spay-procedure.aspx
- Determining the optimal age for gonadectomy of dogs and cats: http://www.parsemusfoundation.orghttps://swbmedia.blob.core.windows.net/swbmedia//2012/11/Root2007gonadectomyOptimalAge.pdf