Colostrum

On the left is human breast milk expressed on day 4 of lactation, and on the right is breast milk expressed on day 8. Colostrum has a yellowish hue.

Bovine colostrum (beestings) next to spray-dried colostrum powder

Colostrum (from Latin, of unknown origin), also known as foremilk, is the milk expressed by the mammary glands of a female mammal during the first few days following delivery of the newborn. Animal colostrum may be called beestings, the traditional word from Old English dialects.

Most species begin to generate colostrum just prior to giving birth. Colostrum contains antibodies to protect the newborn against infection, and immune and growth factors. Colostrum is beneficial for a newborn's growth and immune system in calves and humans.

At birth, the newborn moves from the sterile conditions of the uterus, with a constant nutrient supply via the placenta, to the microbe-rich environment outside, with irregular oral intake of complex milk nutrients through the gastrointestinal tract. This transition puts high demands on the neonate's gastrointestinal tract, which plays an important part in the immune system.

Colostrum contributes to the newborn's initial humoral immunity in calves and humans, and contributes to the growth, development, and maturation of the gastrointestinal tract in calves. Colostrum also has a mild laxative effect, encouraging the passing of a baby's first stool, which is called meconium. This clears excess bilirubin, a waste product of dead red blood cells which is produced in large quantities at birth due to blood volume reduction from the infant's body, and which is often responsible for jaundice.

The importance of colostrum for prevention of infection varies by species. While human infants can be raised on milk substitutes or normal ruminant milk, protected for 6 to 12 months by antibodies from the mother that entered the fetus's bloodstream via the placenta, colostrum intake is crucial for newborn ruminants (cattle, sheep, goats, etc.) Calves denied colostrum almost universally die due to bacterial infection.

Research on possible health benefits and medical applications of bovine colostrum is ongoing. Currently, there is no accepted medical use of bovine colostrum to treat any condition in humans.