Colostrum is the first milk produced by the cow after calving and is rich in immunoglobulins (antibodies), growth factors, and several other nutrients and compounds that promote calf health. It is well-known that colostrum is critical for calf health. Due to a lack of transfer of antibodies across the placenta during pregnancy, calves are born with a naïve immune system and rely almost exclusively on consumption of colostrum for the transfer of passive immunity and subsequent immune system development. Inadequate consumption of antibody-rich colostrum shortly after birth can result in poor immune system development, which is associated with high calf morbidity (illness) and mortality (death) rates during the pre-weaning period. There are three key components to a successful colostrum program: quality, quantity, and timing.
Colostrum quality is determined by assessing immunoglobulin (antibody) concentrations, specifically, the concentration of immunoglobulin G (IgG). Colostrum is considered to be “good” quality if IgG content is greater than 50 g/L. While direct measurement of colostrum IgG levels are expensive and time consuming, there are two tools available that can help producers quickly and economically assess colostrum IgG content through indirect means: a colostrometer and a Brix refractometer. A colostrometer measures specific gravity and a Brix refractometer measures total solids, both of which are have been shown to correspond to IgG content in colostrum. Both are useful tools for estimating colostrum quality, but the Brix refractometer has become popular in recent years because it is less fragile and less sensitive to fluctuations in temperature as compared to the colostrometer. Recent research suggests that a Brix reading of ≥21% is indicative of good quality colostrum. While it is tempting to forego assessment of colostrum using one of these two tools, producers should know that visual appraisal of colostrum quality is highly inaccurate because color and viscosity are not related to IgG content.
In addition to antibody content, producers should also ensure that colostrum is free from harmful bacteria or contaminants. To minimize bacterial growth, fresh colostrum should be fed within 1 hour; if this is not possible it should be stored in the refrigerator (<35°F) for up to 24 hours or the freezer (<-5°F) for up to a year. Safe thawing of frozen colostrum can be accomplished by submerging the container in a warm (<120°F) water bath and feeding within 1 hour of thawing. Using hot water (>120°F) to thaw colostrum can significantly reduce quality by destroying the antibodies.
In addition to quality, quantity of colostrum is also important. Calves should be fed colostrum at a rate of approximately 10-12% of body weight. This is typically around 4 quarts for Holstein calves and 3 quarts for Jersey calves. If a calf will not consume all of its allotted colostrum from a bottle, producers should use an esophageal tube-feeder to ensure all of the colostrum is consumed.
Timing of colostrum consumption is the third component of a successful program. The ability of the calf’s intestine to absorb the antibodies in colostrum greatly diminishes with time, and is essentially nonexistent by 24 hours after birth. Studies show that delivery of two colostrum feedings within the first 12 hours of life can ensure absorption of sufficient quantities of antibodies to develop the immune system. It is generally recommended that the first feeding of colostrum occur within 2 hours of birth and that the second feeding occur within 8-12 hours.
Evaluation of the Program
The colostrum feeding program can be evaluated by testing blood levels of IgG within 24-48 hours of birth. The traditional threshold for evaluating success of passive transfer has been >10 g/L. However, recent research suggests that this threshold should be increased to >15 g/L. As with colostrum, estimation of blood IgG levels can be accomplished on-farm through indirect means using a Brix refractometer. If choosing this approach, producers should verify that their Brix instrument is capable of analyzing blood samples.
Transition Milk & Extended Colostrum Feeding
In a standard colostrum program, calves are fed whole milk or milk replacer after the first two colostrum feedings, usually beginning around 24 hours after birth. However, the process by which the composition of colostrum becomes similar to that of whole milk is gradual and takes several milkings to fully occur. This milk is often referred to as “transition” milk and although its composition is different from colostrum, it still contains significantly greater concentrations of nutritive (fat and protein) and non-nutritive (growth factors, hormones, white blood cells) components than whole milk, which are important for development. Some of the hormones and growth factors found in colostrum and transition milk are thought to have a positive influence on intestinal growth and maturation, which may help calves digest and absorb nutrients more effectively. While there are no concrete recommendations for the feeding of transition milk or extended colostrum feeding, recent studies have shown some benefits to these practices on pre-weaning growth and feed efficiency.
Take Home Message
Quality, quantity, and timing are three key components of a successful colostrum feeding program. All calves should receive two feedings of high quality (>50 g/L IgG) colostrum within the first 12 hours of life (0-2 hours and 8-12 hours) at a rate of 10-12% of body weight. New research related to the benefits of feeding transition milk and extended colostrum feeding is forthcoming, but studies will likely divulge recommendations related to these practices.