Does breeding make Dogs aggressive after their first time?

Question
Hi, I have a labrador? He's 4 years old and very active. I haven't taken him for mating even once.I've seen blood coming out of his private part. I want to know if I should take him to the vet so that he can mate with a bitch. Is it really necessary? I've heard that dogs become really aggressive after their first time. I dont want that to happen. And I've not seen him hump anything or anyone in a very long time now. Should I consider castration?

Answer
There should NEVER be blood coming from your dog's penis! Something is very wrong and he needs to be seen by a veterinarian as soon as possible!

As to breeding him, that is not necessary. Go ahead and have him neutered. Breeding him would (should) not make him more aggressive with people, but it could with other males.... particularly if there are bitches in the area that are not spayed and are in season.