Colostrogenesis: The Formation of Bovine Colostrum
A pregnant cow, about 3-4 weeks before delivery, creates what is called colostrum. It is created by a fluid which is released into the mammary tissue being developed in the mother cow. This fluid contains transforming substances and growth hormones such as progesterone. Progesterone attaches to the cell lining in the mammary gland and inhibits the cells from releasing any fluid into the gland during the pregnancy. These cells have receptors on them that help transfer substances such as antibodies, growth promoters and other hormones from the mother cow’s blood into the mammary gland. These substances help the calf in its development after it is born.
2 days prior to the birth of the baby calf, the hormonal balance in the mother cow changes; many secretions are produced as well as the mammary tissue combines multiple substances together. When the calf is born and the placenta is eliminated, the progesterone levels in the mother cow decrease dramatically. Additionally, the protein-based substance lining the mammary gland is stopped so there are no additional substances transferring from the mother’s blood into the mammary gland. Colostrum is the cumulation of fluid in the mammary gland at the birth of the baby calf. Thus, Colostrum is rich in milk fat, low in lactose content, contains a high concentration of protein, mainly antibodies, as well as a high concentration of hormones such as growth promoters and metabolically active substances.
Six short hours after birth the colostrum changes in its composition. This change is due to maternal reabsorption as well as fluid being removed from the mammary gland. There is replacement fluid for the mammary gland which contains a different composition than the fluid prior to parturition. This replacement fluid is called transitional milk. Bovine colostrum of the highest quality, with the most nutrients, is collected within the first six hours after birth in a single milking of the mother.
While the colostrum in the mother cow are changing quickly after the birth of the calf, the baby calf is undergoing a number of changes in its body. Within the first six hours of life, the calf’s stomach lining does not produce any acid and there are a limited number of enzymes which break down proteins that are ingested.
In the first milking, the colostrum passes through the the stomach and the intestine of the calf without being broken down. Between 6-8 hours after birth, the calf begins to absorb and transport biologically active substances into the bloodstream. Then the stomach begins to acidify as well as enzymes begin to appear. The calf is born with lymphoid tissue that is well-developed which absorbs many biological active substances when the calf milks.