i would steer well clear of supermarket brand tinned foods. In my opinion they are cheap, mass produced crap.
have you thought about making your own at home ? there is heaps of info on home made food on this forum and on the web. do your research, there is plenty of
information out there!
good luck with it, and good on you for rescuing an abandoned dog.
"He is your friend, your partner, your defender, your dog. You are his life, his love, his leader. He will be yours, faithful and true, to the last beat of his heart. You owe it to him to be worthy of such devotion" Author Unknown