Original: Taxonomists who consider domesticated cattle a subspecies of the wild Aurochs should use B. primigenius taurus; the name B. taurus remains available for domestic cattle where it is considered to be a separate species.
Simplified: Taxonomists who consider  domesticated cattle a subspecies of the wild Aurochs should use B. primigenius taurus; the name B. taurus remains available for domestic cattle where it is considered to be a separate species.