Colostrogenesis: the Formation of Bovine Colostrum

The formation of colostrum in the pregnant cow is initiated about 3-4 weeks before parturition when a limited amount of fluid containing small amounts of growth factors and other transforming substances is released into the developing mammary tissue. The process is regulated by a series of other hormones, one of the most important being progesterone, which attaches to special receptors on the cells lining the mammary gland and prevents them from secreting any fluid into the gland during most of pregnancy. About two weeks before birth, these substances influence the appearance of specific receptors on the surface of the cells lining the mammary gland that will facilitate the transfer of materials from the mother’s blood into the gland, including the immunoglobulins (antibodies) necessary to convey passive immunity to the calf after birth and various hormones and growth promoters required to induce and support development of the newborn calf.

The hormone balance in the mother cow begins to change about 2 days prior to the birth of the calf. This hormone change initiates secretions and combines substances together. After the baby calf is born and the placenta is delivered, progesterone levels in the mother drop. The blocking of secretions by progesterone is eliminated; a protein-based substance is created in the mammary gland cells and transfers of substances from the mother’s blood into the mammary gland are stopped. The fluid in the mother cow found in the mammary gland at birth is called colostrum. It contains high amounts of hormones, metabolically active substances and growth promoters. Colostrum also has a high concentration of protein, is rich in milk fat and low in its lactose content.

After birth, one of the most influential factors on the composition of subsequent secretions is physical removal of the fluid from the mammary gland. The removal of even small quantities of fluid triggers the production of copious amounts of secretion from the cells in the mammary gland. Since the transfer of biologically-active substances from the mother’s blood is blocked, replacement fluid will contain primarily substances synthesized by cells in the mammary gland and, thus, will be of a different composition than the fluid originally contained in the mammary gland at birth. The fluid expressed at this time is known as transitional milk. This is further complicated by the fact that the basic composition of the colostrum changes after birth due to maternal reabsorption and does so rapidly beginning at six hours, as can be seen from the table below.10 Thus, the highest quality bovine colostrum, containing the maximum concentration of biologically active substances, is collected in a single milking during the first six hours after parturition. [I:http://www.uniquearticlewizard.com/extras/pics/henageimage0.gif]

While the colostrum changes its composition, the events complement the events of the newborn baby calf. When the calf is born, its stomach lining has very few enzymes to break down ingested proteins and does not make any acid.

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.

Dr. Kleinsmith is the leading expert in colostrum research. Learn more about the colostrum benefits by visiting the colostrum authorities online resources at ImmuneTree.com today!

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