Initiation of milk secretion is called

Initiation of milk secretion is called Lactogenesis.
Lactogenesis is the process of developing the ability to secrete milk and involves the maturation of alveolar cells. It takes place in 2 stages that are secretory initiation and secretory activation.
The process naturally occurs with all sexually mature female mammals, although it may predate mammals. The chief function of a lactation is to provide nutrition and immune protection to the young after birth.