Hi all,
I could do with some advice please.
I take a Friends dog out. Its a 5yr old  boxer x bulldog which was abused by its owner, also attacked constantly by other dogs in the first 12 months of its life. Since then the owner goes through a nightmare every time the dog goes out. Whenever it sees a dog, or a cat it goes into an aggressive state by trying to attack any other dog, even if the dog is a distance away. I have tried to snap her out of it before she goes into aggressive mode but makes no difference. I have tried other things including changing direction, but she still lunges towards the dog, pulling and standing on her back legs. It does not matter what equipment I  use it does not stop this nervous/ or dominant aggression. In the house  she is adorable. The funny thing is , she lives with another dog and cat which she gets on well with!   Can someone advice please?

My rott can get a bit like this and the way I deal with it is to put him in a sit and stand in front of him so I am facing him blocking his view of the other dog.  I then get him to look at me (this takes a bit of practice!) and when the distraction goes past without a show from him he gets a biscuit.  With my boy there is no point in giving him biscuits while he is fixated on something as he won't eat them.  they only become a reward to him afterwards.  good luck

Slow process. You need to start rewarding as soon as the dog sees another dog but BEFORE it has reacted. At first this will most likely be at a great distance then you slowly (over many weeks) move closer. See dog at distance, no reaction,  get treat. (You need to be quick to get the reward in before anything has happened.) A headcollar is the most useful because the head can be moved and what is most important is stopping eye contact.

Have a look at BAT training by grisha Stewart - it's an excellent, gradual approach to teaching the dog to make the right decisions when faced with a trigger (e.g. turn away instead of charge at), and helps the dog relax knowing it has other options than aggression.

Doing some foundation work will be useful too - things like shovelling the dog full of tasty things as soon as he's spotted a dog (but far enough away that he's not bothered by him; that will help build a positive meaning to other dogs to counteract the negative one he has now.  Also a handy little game is a version of Look at That - in basic terms, the dog gets clicked and treated for looking at dogs (again, far enough away that he notices them but isn't bothered).  Pretty soon he'll start to look at them then back at you for a treat, then you can just click that.  It allows the dog to see and observe the trigger (so he doesn't get worried about what the other dog is doing if he can't see them), but turns it into a game which will relax him (and again, there's the positive association of the food).

BAT training uses distance as the reward - extremely effective, more so than food as you work closer (although you can still incorporate treats into the training).  Food can distract a dog a bit too much - one dog I work with would literally walk into the stooge dog if food is on offer because she'll just stare at the food, but using distance to reward good behaviour means she had a fantastic session on thursday that ended with her walking around with my dog quite happily (she has a full bite history with other dogs and used to attack if they got within reach).

The mind boggles as to how 2 such different size/build dogs could produce pups.

Hope you manage to get her out of this habit as it can't be much fun going for a walk and having to scan the horizon for dogs.

Well!! there is a lot to digest and try out. Thanks everyone for your help and support