Edith,

This is very dangerous situation. I know you stated that the thyroid test came back negative, but her behavior is very erratic. It is erratic enough that I would consider investigating other causes for sudden aggression. The following site goes over the medical causes for sudden aggression.
http://k9aggression.com/medical-issues-overview/

This might involve ct scans of the brain and spine and hips to rule out brain abnormalities, growths and pain as potential causes for the sudden aggression.

About the only thing I can see that might be triggering her aggression is a misplaced idea that she needs to protect her "pack" members from other people. However, even that doesn't fit hr charging and biting one of the girls. I can see how the vet getting too close to you and the man approaching your boyfriend might trigger protective aggression, but the other situation doesn't seem to fit that scenario.

However, to stop protective aggression, the humans have to be the alphas in the "pack" (both dogs and human). While I know she has been to obedience class, she needs to go back. Each family member including the boyfriend all need to work with her on obedience. Each time a human gives her a command and she obeys, it reinforces in the dog's mind that the humans are the alpha. As alphas, it is the humans job to do the protecting and not the dog's job. Once the dog sees the humans as the protector, she should stop that behavior. Additionally, have her leashed and each time she growls, or fixates on a specific person, give a tug of correction and a firm low toned "NO" to indicate you will not tolerate the behavior. If she does not stop the behavior, give her another correction.

You need to remain calm in these situations as a dog picks up on your worry and that makes her think she is justified in being worried and protective. So you need to be calm. A muzzle goes a long way toward this. You need to get a good quality basket type muzzle. They usually use buckles or clips to secure the muzzle and are very hard for a dog to remove. Since it doesn't fit tight around the muzzle, many dogs tolerate them better. This will serve to prevent bites and also keep you calmer during training and in social situation.

Everyone should train the dog daily if at all possible. Remember each obeyed command is reinforcement that you humans are the protectors. Before you can get into classes, I am including links to a couple of other sites that teach some good methods of training. Be sure and read both.

http://www.sibes.org/sdo/index.asp~m=article&name=sdo.id.A000232

http://www.luckydogs.info/pdf/Teaching-the-basic-commands.pdf

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The following site is helpful. Be sure and click on the link to the left on obedience. and links on subsequent pages leading to detailed instructions.

http://www.schutzhund-training.com/training_theory.html

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Training works best if you train at least 30 minutes a day (two 15 minute sessions). I would start making your dog work via the Nothing in life is free program (NILF). It is outlined below.

http://www.pets.ca/articles/article-dog_nilf.htm

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You will also want to keep a leash on her at all times initially to grab if she should disobey. I think you will be pleasantly surprised at how well your dog does with training. Dogs like knowing what is expected of them and they love the little paper thin slices of hotdogs that I use for treats while training. Give this a try and see how it works for you.

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In addition, if the situation is not improving using the techniques on the previous website, you may have to consult a professional behaviorist. You can usually find a behaviorist by asking your Vet for a recommendation or you may be able to find one using the following site.

http://www.apdt.com

I hope this information is helpful to you. If you would like any additional information or have more questions please don’t hesitate to press the reply to expert or continue conversation button.

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