This has nothing to do with dominance or your leadership and thinking that way will only set you up for an antagonistic relationship wih your dogs.
As others have said, adding an aversive to an already stressful situation will increase your dog's aggression without warning signs (what you will be punishing are the warning signs of the underlying emotional response, you are not changing the dog's emotional response to the situation) and he is very likely to start associating negative things in his environment wih the mastiff. Indeed, he already is. When you verbally corrected the mastiff the other day your dog reacted with re-directed aggression. You raising your voice was aversive to him, so he did what in dog logic makes sense -> use aggression (a distancing signal) to attempt to remove the thing in his environment that he associates with negative experiences. The mastiff.
Inter-male aggression by fixed dogs towards intact dogs is very common. Intact dogs have (relative to neuters) high levels of testosterone - which, among other things, is a hormone dogs produce when emotionally aroused. Your fixed dog is interpreting this superficially heightened level of testosterone as aggression/arousal (not sexual arousal, emotional) and therefore thinks he needs to defend himself.
You are shooting down positive training, but counter-conditioning your shepherd to the mastiff is the only way you're really going to address the root of the problem. You need to change his emotional response. What sort of positive training have you done? As you have already realized, obedience training, positive or aversive, has very little to do with behavior modification (other than apparently making your dog more sensitive to correction). Also, a huge part of training is building a language and trust between the two of you. Sending a dog to "boot camp," no matter how well renowned, does nothing for either part of that dynamic, and also does nothing to address the problem in context. As you have seen, it has had no effect here.
I would separate the dogs so he cannot rehearse this behavior and to give you more control for training purposes. I think looking for a certified behaviorist is a good idea at this point, the behavior seems fairly rehearsed and exasperated. Behaviorism is currently unregulated, but this website will direct you to folks with true behavioral training and certification.
http://www.certifiedanimalbehaviorist.com/
In the mean time, there are a few good books I would recommend.
"Click to Calm" - Emma Parsons
"Fight!" - Jean Donaldson (this is available from a website called 'dogwise' as an e-book download for around 10 bucks)
"Control Unleashed" - Leslie McDevitt
As others have said, adding an aversive to an already stressful situation will increase your dog's aggression without warning signs (what you will be punishing are the warning signs of the underlying emotional response, you are not changing the dog's emotional response to the situation) and he is very likely to start associating negative things in his environment wih the mastiff. Indeed, he already is. When you verbally corrected the mastiff the other day your dog reacted with re-directed aggression. You raising your voice was aversive to him, so he did what in dog logic makes sense -> use aggression (a distancing signal) to attempt to remove the thing in his environment that he associates with negative experiences. The mastiff.
Inter-male aggression by fixed dogs towards intact dogs is very common. Intact dogs have (relative to neuters) high levels of testosterone - which, among other things, is a hormone dogs produce when emotionally aroused. Your fixed dog is interpreting this superficially heightened level of testosterone as aggression/arousal (not sexual arousal, emotional) and therefore thinks he needs to defend himself.
You are shooting down positive training, but counter-conditioning your shepherd to the mastiff is the only way you're really going to address the root of the problem. You need to change his emotional response. What sort of positive training have you done? As you have already realized, obedience training, positive or aversive, has very little to do with behavior modification (other than apparently making your dog more sensitive to correction). Also, a huge part of training is building a language and trust between the two of you. Sending a dog to "boot camp," no matter how well renowned, does nothing for either part of that dynamic, and also does nothing to address the problem in context. As you have seen, it has had no effect here.
I would separate the dogs so he cannot rehearse this behavior and to give you more control for training purposes. I think looking for a certified behaviorist is a good idea at this point, the behavior seems fairly rehearsed and exasperated. Behaviorism is currently unregulated, but this website will direct you to folks with true behavioral training and certification.
http://www.certifiedanimalbehaviorist.com/
In the mean time, there are a few good books I would recommend.
"Click to Calm" - Emma Parsons
"Fight!" - Jean Donaldson (this is available from a website called 'dogwise' as an e-book download for around 10 bucks)
"Control Unleashed" - Leslie McDevitt
