Veterinary questions? Ask a Vet for Answers ASAP
You are through to Dr Coles. I am a UK based vet. I am sorry to hear you are having problems with your dog. Unfortunately behavioural problems are very common in dogs who are brought from abroad. Often they have been stray or ill treated and unfortunately a lot of the time they are not accustomed to life within a home. Often they have never experienced things that we see as normal - indoor life and objects we see as completely normal can be very daunting for them. Unfortunately it is very sad as many of them have been exposed to awful things and sometimes unfortunately do not acclimatise well to being pet dogs because of this mistreatment. Often they are very fearful and by 6 years old most behaviours are quite ingrained - i.e he has probably learnt to fear people and be territorial/defensive. I would strongly recommend that you start working on this with a veterinary behaviourist, because this is quite a serious issue which will take a lot of work. The rescue should inform new owners if the dog has any possible behaviour issues. Veterinary behaviourists will be able to do video consultations online however often they need a referral letter from your own vet. I would advise that your vet checks him over to ensure he isn't needing more pain relief. He could be quite stiff/sore still and joint pain definitely can make dogs act aggressively. I would also recommend starting him on a supplement such as Yucalm (you can buy this online) to help. You can also use adaptil plugins which are pheromone diffusers. If things do not improve, your vet can also prescribe some stronger medications which work as anti anxiety medications and help to reduce this type of behaviour.