The contribution of hydrolytic enzymes is essential for the remodeling of the involuting mammary gland and the modulation of four metalloproteases (BMP1, ADAMTS6, ADAMTS9, MMP16), involved in the extracellular matrix (ECM) degradation [26], and four peptidases (ANPEP, CPM, LTA4H, PAPLN) in T20 gilts suggests that sustained hyperprolactinemia in late gestation, in the absence of suckling piglets, can trigger proteolytic events of the involution program. This evidence concerns the gene PAPLN and hyperprolactinemia.