**2.1 Gene regulation and milk biosynthesis**

During the lactation, the mammary gland is in charge of the final biosynthesis of milk using preformed elements from other organs (e.g., glucose synthesized in the liver) or compounds synthesized within the mammary epithelial cells (e.g., *de novo* fatty acids). The biosynthesis of milk in the mammary gland is highly regulated for several factors including nutrient supply (e.g., glucose, AA, and fatty acids) and hormones primarily related to hormonal changes during the onset and at the decline of the lactation.
