B vitamins, including B1 (thiamine), B2 (riboflavin), B3 (niacin), B6 (pyridoxine), B12 (cobalamin), folic acid, and biotin, are crucial in energy metabolism. They help convert food into energy, which is essential for a nursing dog who needs to sustain herself while providing for her puppies. A balanced intake of B vitamins ensures that the mother stays energetic and can fulfill her demanding role.