Aggression with other dogs.

Question
Three months ago I rescued a black Great Dane, he has white markings on his chest and feet. He is a wonderful friendly and gentle dog and perfect in the house. He is cuddly and affectionate not food or treat oriented. Even on the lead he walks perfectly. Better than my pedigree Labrador.

Now, he gets on super with my golden lab. They are the best of friends. They play and eat together but when we are out on a walk and come across any other dog or living animal he goes absolupley crazy. He weighs 58-60kg which I realise is small for his breed but he is still very strong and sometimes he is so persistent is getting at other dogs he pulls me over and drags me along. Once he reaches the other dog he attacks and has bitten. It is really affecting my life and quality of walks. My Labrador is perfect and not bothed by anything. I cannot let my Dane off of the lead at all in fear of him running off and attacking another dog. What can I do to sort this out and calm him down. He has clearly been abused before I rescued him and he was known to be used for breeding.

Any suggestions.
Kind regards,
Mr Ian Doddemeade

Answer
Hello Ian:

This may be because he was not properly socialised as a puppy.
You will need to work on behaviour modification.

Look up Counter Conditioning and Behavioural Animal Training (AKA BAT).

These processes work, but I am afraid you will need the help (hands on) of a professional Behaviourist.

Unfortunately I live in Canada now, so am out of touch with whom may be available in your area.