Pasteurizing Colostrum: the next step to controlling disease
The authors are a professor and research associate in the department of dairy and animal science at Penn State. Calves absorbed more immunoglobulins when colostrum was pastuerized.
Pasteurization has been shown to be very effective at killing a variety of pathogenic bacteria including: Salmonella, E. coli, Mycobacterium avium subspecies paratuberculosis, Mycobacterium californicum, Mycobacterium bovis, and Listeria monocytogenes. With proper pasteurization, these bacteria are reduced in both waste milk and colostrum. If you are using pasteurization for waste milk to control the spread of disease, feeding fresh, unpasteurized colostrum represents a break in the system that could allow organisms to spread to your replacement herd. Pasteurizing colostrum can eliminate this weak link and may also improve blood IgG levels and calf health. Bacteria can get into colostrum through contamination from milking dirty udders, reservoirs in dirty milking equipment or colostrum storage containers, and by direct shedding from the udder. We are learning that pasteurization can be used for colostrum in a similar manner as it is used for waste milk. However, there are distinct differences in the way colostrum is pasteurized compared to waste milk.
First, we must remember that the nutrient density of colostrum is different from whole milk. Solids such as fat and protein affect how heat is transferred through colostrum or milk. The fat content of colostrum can often be at least two times that of milk and may be much greater. Protein is often four or more times greater in colostrum versus whole milk. In addition, colostrum has high levels of immunoglobulins that require different heat levels and treatment than those used for milk. Early attempts at pasteurizing colostrum using the same time and temperature used in pasteurizing whole milk were largely unsuccessful due to the large reduction in immunoglobulin levels or the creation of a thick, pudding-like mass that was hard to feed and even harder to clean out of pasteurization equipment. In the past few years, research has studied how to best pasteurize colostrum while maintaining its quality. Since colostrum can be quite varied from cow to cow, it is unlikely that a single definition of time and temperature can be found for true pasteurization for all colostrum. However, a study using a wide variety of colostrum samples conducted at Penn State and published in the Journal of Dairy Science early this year showed that, on average, heating colostrum at 140°F for 30 minutes is the optimum combination to reduce bacteria counts without affecting colostrum IgG levels or viscosity.
Other research from the University of Minnesota showed that if higher levels of disease-causing organisms are present in the colostrum, heating to 140°F for 60 minutes will give a more reliable kill of these harmful bacteria; however, slightly more IgG may be lost in the process. Based on the different characteristics of colostrum compared to waste milk, researchers have determined that batch pasteurization is the only way to successfully pasteurize colostrum. In addition, consistent heating is critical, because once temperatures get over 140°F (60°C), IgG proteins coagulate and IgG levels in the processed colostrum drop. Therefore, a reliable pasteurizer that has good temperature controls is recommended.