Timing is Vital for Obtaining Quality Cow Colostrum
September 3, 2009; By Dr. Anthony Kleinsmith
Filed Under: Bovine Colostrum Colostrum First Milk
Time of Collection
True colostrum must be obtained in the first milking taken during the 6 hours after birth of the calf and such colostrum is not “composed mainly of blood and mucus without the full balance of other components”. In fact, just the reverse is true.
Many years ago, what was then called the United States Department of Health defined colostrum as the "milk" collected in the first six milkings after birth. This was done to keep colostrum out of milk intended for human consumption since it was believed then that it was only suitable for consumption by the calf. However, science has now significantly advanced our understanding of what colostrum really is, how it is formed and the many benefits that it can convey to humans as well as calves. Apparently the advances in our scientific knowledge have either not reached New Zealand or they refuse to accept scientifically substantiated and published facts.
The formation of colostrum in the pregnant cow is initiated about 3-4 weeks before parturition (birth) when a limited amount of fluid is released into the developing mammary tissue containing small amounts of growth factors and other transforming substances. 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 fluids 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 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 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.
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 at birth, 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. This fluid is known as “transitional milk”. This is further complicated by the fact that the basic composition of the fluid changes after birth and does so more rapidly beginning at six hours due to maternal reabsorption of the biologically active substances. 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 birth.
