Abstract: The present invention provides a method of determining the susceptibility of a dog to liver copper accumulation comprising detecting the presence or absence of (a) a polymorphism in the GOLGA5, ATP7a or UBL5 gene of the dog that is indicative of susceptibility to copper accumulation and/or (b) a polymorphism in linkage disequilibrium with a said polymorphism (a), and thereby determining the susceptibility of the dog to liver copper accumulation. The invention also provides a foodstuff comprising copper at a concentration of less than 21 mg/kg dry matter for use in preventing a disease attributable to liver copper accumulation in a dog having genetic inheritance of the Labrador Retriever breed.