My dog's becoming agressive / protective

Why are you so quick to dump the dog? So many owners have the mentality that its okay to get rid of the dog. Dogs are not disposable.It makes me sad to hear those words over something  that is probably easily fixed.

She's not being quick to dump the dog at all!  She posted here for help, not to be told dogs are not disposable.  She has a right to be concerned with the dog's sudden change in behavior.
 
jrsmom, I am not a behaviorist and have no suggestions for you other than to seek out a professional behaviorist and get this nipped in the bud immediately!  If you cannot, depending on his behavior and how a behaviorist evaluates your dog (Note the word behaviorist NOT trainer), solve the problem, and he persists, you COULD try to rehome, but chances are this behavior would continue elsewhere, and if worse comes to worse euthanasia may be the route you have to go.
 
However, your dog is young, if this behavior is rather recent, there IS a chance to rectify it.  The only reason one would be unable to "Cure" this behavior, so to speak, would be if he had some neurological imbalance.
 
Aside from a behaviorist, take him to the vet, have some bloodwork done, and perhaps even an MRI.  Things like tumors, lesions, or pressure on the brain can cause these new behaviors

Labs are a late-maturing breed, so don't discount the possibility that he is just becomong an adult.  At the time of social maturity, many dogs decide, when guests come, that this is our pack, and you are an intruder.  So, they sound the alarm. 
I would hate to see you lose a wonderful dog who is simply alarm barking.  Any sudden change in behavior is worth a vet visit, since there are cases where dogs develop hypothyroidism, or some other disease process, that can cause aggressiveness.  But, IMO, after you rule out those things, get a good trainer or behaviorist to come and observe your dog. 
In the meantime, crate him when guests come, so you won't be yanking and yelling (not saying you have done this, but some folks do, because of embarrassment).  That makes the situation worse. 
If you need to find a trainer, these sites have listing:
[linkhttp://www.apdt.com]www.apdt.com[/link]
[linkhttp://www.clickertraining.com]www.clickertraining.com[/link]
If you aren't aware what positive or clicker training can do, go here and check out the videos:
[linkhttp://www.clickertrainusa.com]www.clickertrainusa.com[/link]
 

Thanks everyone.  I knew when I posted that I"d have some jerk tell me I was being unfair to my dog.  I'm not new to forums, so was prepared.

I'm not trying to dump a dog.  I've never dumped a dog in my life, and I've owned several.  I love my doggie.   But, I can't bear to think what might happen if a visitor gets bit by my dog.  Or worse, what if my sister comes over with her children and my dog bites one of them?  

Our dog was just at the vet for his yearly checkup.  That was the first time I've ever see this behavior - he growled, raised his hair and they muzzled him. 

Xeph and spiritdogs - I was thinking what you've written.  Thank you.  I really think this is protective behavior - he's just now becoming a mature adult and he's protecting his family.  As I live in the country, I would like a dog that barks to alert us to visitors.  I just don't want him to take it further.  This behavior IS new.  The second time I saw this behavior was when my son was in the house and I was in the barn.  Our mail carrier approached our house on foot with a package (very rare- she delivers by car to our mailbox) and the dog stopped her before she was able to reach the house.  He didn't approach her, but lowered his head and growled.  I came out of the barn just as he started, but he kept her there until I saw what was happening and called him.  He immediately left her.  There have been 2 more incidents, both with people arriving but both times he's refused to back down unless my husband and I have actually reached him and touched him.  I should add that after each incident he's then happy to see the people. 

For now we've decided to keep him inside or penned outside unless we're with him outside.  We're going to also get some brave people he doesn't know well to come over and work on training him.  We may look into a behaviorist if that fails. 

Hey Jrsmom,
We went through something very similar with our boy. We had to call a behaviourist who basically told me in no uncertain terms that even though I thought I was in charge, I wasn't! So we're working on it. I got a lot of great advice/tips through this forum as well. (see the thread "fear aggression" started by Trilby999 June 15) Lots of good advice for the op and me. Just wanted to wish you well, as I know how awful it feels to worry about your dog possibly biting someone.

I was just stating my opinion. You were the one who wrote " is it time to get rid of him". I don't appreciate being called a jerk. I didn't call you a name.IMHO.

First let me say that I am truly sorry that you are going through this. I have young children in my house and I would be quite beside myself should one of my dogs pose a threat to them.
 
Second, I would get a behaviorist (not a trainer) in your house IMMEDIATELY!! You need to have someone with experience come in and tell you how to handle the situation so that no one gets hurt until a decision is made on what to do with him.
 
In the meantime, I would assume - in every situation - that the dog may potentially strike out. That may mean getting a soft-sided muzzle when he is loose. If he doesn't get aggressive, you are no worse for the wear. But if he does, you need to be prepared to take appropriate action.
 
You have a serious issue on your hands... please don't put your family at risk because you think you know your dog.  Don#%92t let anyone make you feel bad about thinking of rehoming him.  Unfortunately that is not going to be easy and usually isn#%92t an option for a dog that has show some aggression.  You don#%92t want to just rehome this dog where he can potentially hurt someone else.  You would need to be very specific and honest about his issues and be sure that new home is quite capable of changing his behavior (if you could find someone willing to take him on).
 
Now with all that said, I do believe you can correct this behavior and although it will take some time, dedication and patience it can be done - with professional help. 
 
I cannot stress enough how you need to never leave any dog unsupervised with Children, NEVER!  AND.. PLEASE DON#%92T ALLOW CHILDREN TO RIDE YOUR DOG THAT IS PLAIN DANGEOUS AND UNFAIR TO THE DOG!!

FWIW, I've frequently seen dogs hit an age...usually about two...when they suddenly become very protective of the home. It's not abnormal, but it does have to be managed, and I would strongly echo the sentiments about hiring professional help BEFORE it escalates.

One thing I've found very successful is to teach the dog a "place" command. I have a square wooden platform that I use as "place," though you can really use anything, and I have taught my dog to "go to place" on command. She must stay on place until I release her with the command "free dog." When you get a rock solid place command, you are in a great position, because you can send the dog to place as soon as the dog alerts you to someone coming, and it prevents the opportunity for problems.

My dog is very protective of my house, but I didn't want to lock her away every time a worker came or the cable guy came, because I live alone and don't want strange men in my house and my dog locked away where she can't protect me when I need her to. But I can send to her place and she'll stay there the whole time they're working. She'll watch them intently, but won't move off that board until I release her. Usually, I send her to place, then I allow her to briefly greet the person with a "Come say hello" command, then I send her back to place. This shows her that I am okay with having the person in my home, then puts the dog out of the way so no harm can be done.

Putting the place board where the dog can see who's coming also tends to make the dog less upset because this way they can see what's going on rather than feeling like there's some hidden threat sneaking up on them. So the dog gets to do its job (keeping an eye on things and protecting its home) without having to do the charging/lunging thing.

We do this in class with 30 dogs, and we have actually had cats walk by all the dogs on place boards and the dogs don't move. We do exercises where 25 dogs will be running around playing while five dogs must stay on their place boards even as the dogs run and play around them. If you can train place with distractions, it is one of the best commands you will ever use.

Training will also establish YOUR dominance, so your dog understands that you get to decide who comes in, not them. If your dog feels there is no strong alpha in the house, the dog will try to take on that role -- and, in fact, dogs can be even more stressed if they feel they have to be alpha because no one else is doing that. As alpha, you should be able to call your dog off without grabbing or pulling -- and if the dog won't listen, more training is needed.

Yes, the situation is serious enough that you need to get professional help. But don't give up on the dog yet -- I've seen this problem hundreds of times, and 99% of those times, it's been relatively easy to fix.

Good luck with it!

Jan

luvmyswissy, I'm sorry, but I think you are overreacting to this, given that this is a dog that is exceptionally tolerant of children and the childrens' friends.  The only time I might have reservations is if a *new* friend comes by.  And, the situation can be managed by proper introductions and training.  I LOVE Jan's suggestion, but it does require a commitment to train to that level.  IMO, that is the better solution.  It keeps the owner in control (which is what the odg really wants anyway).  This seems to be a *normal* dog, who is just showing characteristics of social maturity and pack behavior.  He now just needs to learn that he is to warn only, and that the humans will handle anything he is warning them about.  In my house, the dogs warn with barking.  But, the next thing they hear is "thank you".  Then, they must stop barking and come to me.  "Leave it - Come"
 
And do keep the kids off the dog's back - it really isn't safe. 

Thanks all.  We've now had almost 2 weeks without another incident.  He's growled a couple of times when cars have approached, but always followed our commands to come and then was fine.   We'll continue with our training, and hope that he just continues the barking, then leaving the person alone.  (Hope, but be attentive!)  Since I DO live in the country and am alone during the day, we do want a dog that alerts us to strangers, so in the past we've praised for the bark at the same time we've called him to us.   It's my hope that maybe he just wasn't feeling well those couple of weeks during the incidents and overreacted to strangers. 

As to riding the dog - Yes I know it isn't safe.  I understand everyone's concern.  I should say the kids don't really ride the dog - I was exagerating - but the lay on him when he's laying on the ground.  He loves being with them.