Colostrum is a fluid produced by the pregnant cow prior to giving birth to her calf in readiness for the calf at first suckling. Calves are born with little to no immunity and colostrum provides the calf with antibodies that protect it from infectious diseases. This transfer of antibodies from the cow to the calf is referred to as ‘transfer of immunity’.
In addition to antibodies, colostrum also contains white blood cells, anti-microbial factors, growth factors and nutrients. The strongest concentration of these constituents and highest quality of the colostrum is present at birth.
A refractometer can be used to measure the level of antibodies in colostrum indirectly. Readings of 22% or greater on the refractometer’s Brix scale indicate good quality colostrum. The more antibodies (mainly immunoglobulin IgG) in the colostrum, the higher the quality (good quality colostrum contains >50mg IgG per ml).
The calf’s intestine is best able to absorb these large antibody molecules immediately after birth. From then on, absorption ability decreases rapidly within 6 hours and stops completely within 36 hours of birth. However, continuing to provide the calf with colostrum for 2-3 days after birth has been shown to increase passive immune function, improve absorption through the gastrointestinal tract and enhance the calf’s metabolism. This is particularly relevant in the dairy industry where calves are removed from their mother soon after birth and fed colostrum manually.
Bibliography
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