Jo, do you mean he goes off when he sees other dogs? This is how my my dog is also, changing her food didn’t help. She is also a great dog until she meets another dog at the walking trail. She is what you call “leash aggressive” and what collar I have on her makes a difference. A halter is the best with a choke collar(cannot use at all!) being the absolute worst. Gentle leader works with walking correctly but seems to spark her leash aggression. If she could just run up to everyone loose, she would be perfect but in the real world, that’s not possible. On the leash, she pulls toward any dog she sees as soon as they are within sight and when the pass she goes CUJO! I MUST put a treat in front of her nose and stand between the other dog and her. Allowed to visit, she absolutely LOVES all other dogs which to my human brain is senseless behavior but that’s how dogs are. You can research “leash aggression” and see if that’s what her issue is. All I’ve been able to do so far is each time we pass a dog is to focus her attention to me with a treat/food. I assume that eventually she’ll get it…I hope so anyway because it’s maddening…UGH! We have been walking at the park since January and still she’s not getting it although she now ignores 99% of the people out walking, jogging, skating, baby strollers etc.
A good dog food is important for sure but it may not help much with the aggressive behavior…socializing baby steps is about all you can do.
