For some reason my computer isn't allowing me to open any pdf files, and I am dying to read the whole article.
This was the study that Dr Zink referred to 2yrs ago when I attended her excellent seminar.
Behavioral and Physical Effects of Spaying and Neutering Domestic Dogs
Summary of findings detailed in a Masters thesis submitted to and accepted by Hunter College by Parvene Farhoody in May, 2010.
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Another interesting and ongoing study. Results are not what I would have expected to be honest.
Including a difference in bone length was found between neutered and intact dogs, suggesting that neutering has an effect of increasing bone growth. I wonder if this affects bone density at all.
Summary
The above data is just a small sample of the significant data that were determined in this study. By using large a sample of dogs than any used previously to examine behavior in dogs, we found significant correlations between neutering dogs and increases in aggression, fear and anxiety, and
excitability, regardless of the age at which the dog was neutered. There were also significant correlations between neutering and decreases in trainability and responsiveness to cues. The other three behavioral categories examined (miscellaneous behavior problems, attachment and attention-seeking behavior, and separation-related behavior) showed some association with neutering, but these differed more substantially depending on the age at which the dog was neutered. The overall trend seen in all these behavioral data was that the earlier the dog was neutered, the more negative the effect on the behavior. A difference in bone length was found between neutered and intact dogs, suggesting that neutering has an effect on bone growth, which may be related to other orthopedic effects documented in the literature. Examination of changes in bone length of gonadectomized dogs is continuing.