Final answer:
Breast milk composition changes during lactation and feeding. Colostrum, transitional milk, and mature milk are produced in the first postpartum days. Foremilk quenches thirst, while hindmilk satisfies the infant's appetite.
Step-by-step explanation:
The composition of breast milk changes during the first days of lactation and in the course of a single feeding. In the final weeks of pregnancy, colostrum is produced, which is high in protein but contains less fat and glucose than mature breast milk. After childbirth, breast milk is secreted and consists of colostrum, transitional milk, and mature milk.
Colostrum, produced in the first postpartum days, provides immunoglobulins that increase the newborn's immune defenses. Transitional milk is the transition phase between colostrum and mature milk, and mature milk changes from the beginning to the end of a feeding. The first milk at the beginning of a feeding is called foremilk, which quenches the infant's thirst, and the milk at the end of a feeding is called hindmilk, which satisfies the infant's appetite.