colostrum
On the left is milk expressed on day 4 of lactation, and on the right is breastmilk expressed on day 8.
Colostrum is the first thin watery fluid secreted by the mammary glands in the breast after the birth of a child. Although low in fat, colostrum is rich in protein, including antibodies which are important in giving temporary passive immunity, notably in cattle and other ungulates. True milk is produced several days after birth.
