I don't want to step on anyone's toes here, but it might be a good idea to teach a command like "Drop it." When they are refusing to give up what is in their mouth to the Alpha, they are refusing to let you be the alpha. When the dog tightens his grip on the food he's taking charge over his owner. You don't want a dog that's going to fight with you over having something dangerous in its mouth, if it happens.' Each of my dogs are taught drop it and I can easily remove something from their mouths without worry about being bitten 
One excersize I do with my dogs is to give them a treat, such as a bone, allow them to have it for a moment, then take it, pretend to chew it as well for a minute or so, and then give it back. The bone goes back and forth so that they are comfortable with sharing and they know that its going to get given back to them if they can have it.
I guess I just feel bad that so many people are bitten by their bullies. I never realised it happened so much!
One excersize I do with my dogs is to give them a treat, such as a bone, allow them to have it for a moment, then take it, pretend to chew it as well for a minute or so, and then give it back. The bone goes back and forth so that they are comfortable with sharing and they know that its going to get given back to them if they can have it.I guess I just feel bad that so many people are bitten by their bullies. I never realised it happened so much!
