Mating male dog exhibiting aggressive behaviour towards visitors in the house

Question
QUESTION: Hi, I have a male Pit Bull Terrier who has mated with a female dog for the first time recently. He has been trained by a pfofessional trainer for 6 months before I got him. I have had him for 16 months now. He is 22 months old.
We bought the bitch on heat into our home 3 days ago.We allowed them time together both supervised and unsupervised.
A female friend my dog is familiar came to visit went to play with my dog as she usually does and he embarked on an attack.
He was on a chain so he only superficially scratched her face with his teeth thankfully.
We were all very shocked as he has never shown any aggression before.
Another male friend visited later on in the day and the dog was loose. He attacked his leg and latched on tearing his trousers and drawing blood on his leg.
In my shock and terror I grabbed the dog by the neck and tried to prise his mouth open where-upon he bit me.
He was then chained up outside and threatened someone else he is familiar with when they tried to walk into a stairwell leading into he house, but failed to reach as he was chained.
Today I took him out and he was fine just like his old self.
The bitch has now left our home.
Is it something to do with this first mating or having had the bitch in my house.
I have approached a trainer about this problem.She insists that I must not physically punish the dog and I must not give him access to my guests until I have greater control over the dog through training using positive non punitive training methods and suggested that I castrate him. I would be grateful for your in-put


ANSWER: This is NOT typical for a male after mating, but it can happen, it's an example of extreme hormonal stress. I very highly suggest that he is immediatly neutered, and that you do not allow him to breed again. This can, and most likely will, be a trait he passes on to puppies. This will also, get worse every time if allowed to continue.

I agree with the trainer, do not pysically punish the dog as he has no idea what he is doing, he feels he is protecting his right to mate by not allowing anyone else access to the area where the bitch is. Punishing him physically will only encourage the idea- basically reinforcing the "me against them" idea in his head.

The only thing you can do at this point is to work with an aggression specialist on positive reinforcment training, NEUTER HIM, and let his hormones die down. The more training you do with a dog, the more control you are going to have over him- I know that sounds like everyone should know that, but you would be suprised. Even little things like basic obedience commands reinforce your dominance. Continue to train, continue to respect him but do not act afraid of him, and do NOT allow him access to anyone without a muzzle on until you have better control and he has been neutered.

I am so sorry this is happening, but thank you for not reacting with your gut and hurting him, or abandoning him as many owners would have the first time he showed agression.

---------- FOLLOW-UP ----------

QUESTION: The trainer I have approached has told me that she is not an aggression specialist.However she is the only dog person available in my area and seems to be knowledgeable.
She told me at this stage we cannot be sure exactly why the dog is displaying aggressive behaviour. She has taken a detailed account of my dogs life and medical history as well as a how I live with my dog.
She has suggested that I may have inadvertantly given him the wrong impression of his position in our householdand now as he moves into maturity he may be asserting himself.
As well as positive training she has suggested that I make changes in the way I live with my dog e.g not leave his food down all the time and not allow him access to my bedroom except on invitation to name two.
She also suggested castration ASAP.
She has stressed that she will only help me if I agree to deny my dogs access to guests until he is totally under control.
Does that sound right to you?  

Answer
I agree with what she has said, it is a basic training program called the "nothing in life is free" program. Its a phenominal tactic of teaching your dog that he has to ask permission for EVERYTHING from you. It knocks him down a few pegs in the pack order and helps establish yourself as alpha. If she has watched the two of you interact and feels that this is a dominace issue more then a hormonal issue (or a combination of the two which is perfectly logical) then this is the perfect program.

She should insist that he works for everything. Sit, down, stay, etc... for toys, treats, food. He should sit and wait to ask for permission to enter a room, or to go for a walk. He should never have anything handed to him, and he should never DEMAND anything, or he won't get it. Denying him access to the "alpha" sleeping area is another helpful tidbit.

I absolutely agree with not free feeding. And if I were your trainer, I would require you to agree to neuter and deny access to guests until he is under control as well. I think everything sounds right :)

Good luck!