What is the medical term for a cow that has a "sunken spine"?

The medical term for a cow that has a "sunken spine" is kyphosis. Kyphosis refers specifically to an exaggerated curvature of the thoracic spine, which gives the appearance of a hunched or sunken back. This condition can occur in various animal species, including cattle, and it can result from various factors such as nutritional deficiencies, genetic predispositions, or health issues that affect the skeletal structure.

While lordosis refers to an inward curvature, often seen in the cervical or lumbar regions, and scoliosis involves a lateral curvature of the spine, neither accurately describes the appearance of a sunken spine. Flatback refers to a specific conformation often seen in livestock that signifies a straight or horizontally aligned back without the curvature typical of kyphosis. Therefore, kyphosis is the correct term for the condition described as a "sunken spine" in cattle.