Q) At what age should a dog be altered?
A) Altering is most commonly done either "early" (8 weeks to 4 months) or "normal" (around 6 months) or "late" (1 years or later).
Early altering is appropriate for pet dogs, or working dogs which do not need complete muscle development. This would include basically all dogs but weight pull dogs. It is absolutely vital that shelters and rescues placing young dogs with the public utilize early age s/n to ensure altering of adopted animals. The practice is not without controversy. To educate yourself about both sides of the issue, read the following:
Pro Early Age Altering Article
Sport Dogs And Early Age Altering
AVMA Statement on Early Age Altering
Altering your dog between 6 and 9 months of age seems to be a completely safe option. This is when I spay my bitches; generally right before their first heat. This keeps their "girly parts" nice and small and does not seem to affect their musculature in any way. I have never had any of my spayed females get fat either. Spayed females getting fat is a myth. However, I will say that I have had more than one spayed female develop incontinence problems which can be a real pain.
With my male dogs which are going into police detection work or pet homes, I neuter them between 6 and 9 months. This has proved satisfactory for me. Dogs which are going to be worked in weight pull but not bred I would not neuter until they were closer to 24 months.
Q) Does altering a pit bull make them less dog aggressive?
A) Yes and no.
The sooner a male dog is altered, the better your chance that male to male aggression will be limited. But stopped? No. The rule of thumb is, "better neutered than not neutered" as far as dog aggression goes, but if you wait until the dog is 10 or 12 months (or later) to neuter, the effect will be negligible. However, reducing testosterone at any time can't help but reduce tension and sexual frustration in a male dog.
Spaying females does not appear to have any effect on dog to dog aggression.
Q) Does altering a dog or bitch make them healthier?
A) Statistically, spaying a bitch before her first heat will help her avoid mammary tumors. However, neutering a male increases their risk of prostate cancer/infection. For an interesting article (by a veterinarian) on this subject, click here.
Q) Does neutering a male dog make him "stay home"?
A) A fence makes your dog stay home. To own a dog without a securely fenced yard (or part of a yard) is simply irresponsible in my opinion. An unneutered male can "go crazy" when he smells a female in heat in the neighborhood. Dogs normally contained by a fence or kennel can suddenly dig, jump or climb their way out. And in-heat females can be just as bad. Their desire to find a male is as strong as the male's desire to find the female.
Q) Why should I spay my female dog?
A) Because the breed is being destroyed by over population. Unless you have years of experience with the breed, are willing to do health testing, titling and only breed when you have a waiting list - then please, PLEASE, don't breed your dog. EVERY person that sells pit bull pups to the public is part of the PROBLEM - not part of the solution.
Besides that, a spayed bitch is SO much nicer to live with! No messy heats. No male dogs camped outside your front door.
Q) Why should I neuter my male dog?
A) If you can keep your male from breeding, if you can keep him from being sexually frustrated by being around females in heat which he can't breed, if you can be responsible enough to not succumb to the temptation to "just breed him once", then not altering can be an option.
I am not convinced that unaltered dogs are any more aggressive or prone to bite than neutered dogs. I think what the statistics show is that DOG OWNERS who allow their dogs to get into trouble are much more apt to have failed to neuter their animals. As always, when dogs bite or otherwise get in trouble, the dog is not the issue - ownership management is the issue.