Copper Proteinate

Copper is needed to use iron and to build connective tissue and coat pigment. In this form it’s bound to amino acids. AAFCO says these bound forms are thought to work better than inorganic compounds, though how much difference that makes in a complete food isn’t settled.

There’s a live debate here. Some dogs build up copper in the liver, and some breeds are known to be prone to it. Veterinary authors have asked whether guidelines for copper in dog foods should be revisited. If your dog has liver disease, ask your veterinarian about copper in its food.