The present invention provides a method of testing a dog to determine the susceptibility of the dog to liver copper accumulation, comprising detecting in a sample the presence or absence in the genome of the dog of one or more polymorphisms selected from:(a) Chr22_3167534 (SEQ ID NO: 144), Chr22_3135144 (SEQ ID NO: 145), Chr20_55461150 (SEQ ID NO: 146), ChrX_120879711 (SEQ ID NO: 147), Chrl9_6078084 (SEQ ID NO: 148), Chrl5_62625262 (SEQ ID NO: 149), Chrl4_39437543 (SEQ ID NO: 150), Chrl5_62625024 (SEQ ID NO: 151), Chr3_86838677 (SEQ ID NO: 152), Chr24_4011833 (SEQ ID NO: 153), Chrl8_60812198 (SEQ ID NO: 154), Chrl0_65209946 (SEQ ID NO: 155), and the CGCCCC repeat at chromosome location 22:3135287；(b) one or more polymorphisms in linkage disequilibrium with a said polymorphism (a)； and/or(c) Chr32_38904515 (SEQ ID NO: 156), Chr8_4892743 (SEQ ID NO: 157) and Chr8_4880518 (SEQ ID NO: 158).
