Final answer:
Breast milk changes in composition throughout a feeding and over the course of lactation. It contains foremilk and hindmilk, which have different purposes and nutritional content. Breast milk is better absorbed by infants compared to cow's milk.
Step-by-step explanation:
Breast milk changes in composition throughout a feeding and over the course of lactation. The early milk, known as foremilk, is watery, translucent, and rich in lactose and protein, which quenches the infant's thirst. The milk delivered at the end of a feeding, called hindmilk, is opaque, creamy, and rich in fat, satisfying the infant's appetite. Breast milk also undergoes transitional changes from colostrum to mature milk, with mature milk being dominated by whey and containing more lactose but less iron than cow's milk. However, breast milk is better absorbed by infants due to its composition and the proteins in cow's milk being difficult for infant digestion.