Prior to the let-down reflex, the mammary glands secrete a yellowish fluid called that has less lactose than milk and almost no fat. colostrum bilirubin prolactin meconium

Prior to let-down reflex, the mammary glands secrete a yellowish fluid called colostrum that has less lactose than milk and almost no fat. Colostrum is normally the first form of milk produced by the mammary glands immediately after the delivery of a new born. It contains large numbers of antibodies called secretory immunoglobulin that help protect the mucous membranes in the throat, lungs, and intestines of the infant. 

The organelle that contains digestives enzymes that break down waste material and debris in the cell is the lysosomes. The organelle inside the animal cells that are fully membrane-bound. They are not present in the red blood cells. Other organisms have other type of organelle for the specific functions.