Colostrum
The first “milk” produced late in pregnancy and the first few days after birth. Colostrum is especially high in growth factors and immunoglobulins – which are beneficial for the newborn.
Colostrum from immunized cows has been used experimentally to treat gastrointestinal infections. More generally, colostrum is used as a supplement to enhance general immunity, health and athletic performance. Although probably useless as a performance enhancer, there’s some data to support its use for general health/wellness, although studies have used amounts much larger than many supplements provide.