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.
About 2 days before birth, the hormonal balance begins to shift, initiating the production of copious secretions and switching on the ability of cells in the mammary tissue to synthesize various substances, including lactose. At birth, when the placenta is eliminated, progesterone levels fall dramatically in the mother and its inhibitory control of the secretions is removed. Simultaneously, a protein-based substance develops in the cells lining the mammary gland that essentially blocks any further transfer of substances from the mother’s blood into the gland. The composition of the fluid in the mammary gland at birth is that of true colostrum and reflects the functional changes that have occurred in the gland up to that time; it a) has a high protein concentration, most of which is IgG; b) contains the highest concentration of growth promoters, other hormones and additional metabolically active substances; c) is low in lactose content; and d) is rich in milk fat.
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. [I:http://www.healthymealsrecipes.com/wp-content/uploads/2009/11/DrAnthonyKleinsmith0.gif]
The rapidly changing composition of colostrum in the mammary gland of the mother fits together very well with events that happen in the body of the newborn calf. During the first six hours of life, the calf’s stomach lining does not make any acid and there are very few, if any, enzymes present that can break down ingested proteins. Complete first milking colostrum also contains substances that inhibit the action of some enzymes.
When the calf ingests the first colostrum milking, the enzymes travel through the stomach and intestines without having been broken down. After 6-8 hours after birth, enzymes in the calf’s stomach begin to appear in addition to the stomach beginning to acidify.
Dr. Anthony Kleinsmith is an expert in colostrum research. Learn more about the colostrum benefits by visiting the colostrum authorities website at ImmuneTree.com today!
