Calcium is the most abundant mineral in the body and is required in tightly regulated amounts — both deficiency and excess cause problems. AAFCO sets a minimum (~0.6% DM for adult dogs, 1.0% for growth) and a maximum (~2.5% DM). The calcium-to-phosphorus ratio matters: 1:1 to 2:1 is the target band. Large-breed puppies are especially sensitive — excess calcium during growth is associated with developmental orthopedic disease, so foods labeled for large-breed growth have controlled calcium ranges. Ash content is a rough proxy because most ash IS calcium and phosphorus.