Newborns have very small digestive systems, and colostrum delivers its nutrients in a very concentrated low-volume form. It has a mild laxative effect, encouraging the passing of the baby's first stool, which is called meconium.
Colostrum is known to contain antibodies called immunoglobulins such as IgA, IgG, and IgM. Colostrum also contains a number of growth factors, such as insulin-like growth factors
Human milk contains two types of proteins: whey and casein. Approximately 60% is whey, while 40% is casein. This balance of the proteins allows for quick and easy digestion. If artificial milk, also called formula, has a greater percentage of casein, it will be more difficult for the baby to digest. Approximately 60-80% of all protein in human milk is whey protein. These proteins have great infection-protection properties.
During the first few days after delivery the breast produce colostrum. This is a thin yellowish fluid which is the same fluid that leaks from the breasts during pregnancy. It is rich in protein and ingredients that help the baby's immune system. Colostrum also helps the newborn's digestive system to grow and function properly.