graciefan, do you mean this one?
http://www.naiaonline.org/pdfs/LongT...uterInDogs.pdf
My male Dobe lived to 13 and was never neutered. We did not have a contract. He was a true gentleman as well. He would never wander off our property(unless he was chasing a squirrel, cat or rabbit). There was a mixed german shepherd female in the house across the street who was crazy about him, but he never wandered over there or tried to jump the fence. So from my personal observations I did not witness any aggressiveness or wandering that was foreseen by different vets from the day I got my dog as a pup. I do believe there is a monetary reason behind why vets encourage neutering aside from population control.
Now, with a contract and concerning reputable breeders who go to great lengths to improve and protect their lineage, I believe in abiding by those rules to have the dog neutered or spayed. My next Dobe will be a female and I plan to have her spayed.