by Jud Heinrichs and Coleen Jones
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
An unexpected finding of the research studying pasteurized colostrum was
that calves fed pasteurized colostrum absorbed more IgG. In a Minnesota
study, 24-hour serum IgG was 22.3 mg/mL in calves fed pasteurized
colostrum compared to 18.1 mg/mL in calves fed raw colostrum. Apparent
efficiency of IgG absorption was also improved in the calves fed
pasteurized colostrum (35.6 versus 26.1 percent).
This phenomenon was observed in two different experiments at Penn State,
as well. In one study, calves fed colostrum heated at 140°F for 30
minutes had serum IgG of 22.6 mg/mL at 24 hours compared to 19.6 mg/mL
for calves fed raw colostrum. The higher blood IgG levels remained for
the first five weeks of age. Absorption efficiency was 33.2 percent for
pasteurized colostrum and 27.7 percent for raw. In a second Penn State
study, calves fed pasteurized colostrum had blood IgG levels of 26.7
mg/mL compared to 20.2 mg/mL at 24 hours of age for calves fed unheated
colostrum. Efficiency of absorption was 43.9 percent and 33.9 percent
for pasteurized and raw colostrum, respectively.
In these three studies, feeding pasteurized colostrum increased 24-hour
serum IgG levels by 25 percent and absorption efficiency by 28 percent
compared to feeding raw colostrum. Improving absorption efficiency can
have huge impacts on calves as they are able to attain significantly
higher blood levels of IgG when fed the same quality of colostrum. Based
on past research, we know that increasing 24-hour blood IgG levels can
have significant positive effects on calf health.
On a practical basis, colostrum from the cow that calved today will have
to be harvested, pasteurized, and cooled down before feeding. As a
result, most calves probably will not receive colostrum from their dam.
Instead, pasteurized colostrum will be stored (refrigerated if a large
herd, frozen if a small herd) to be used for the next calf that is born.
Calves will still be fed colostrum produced by cows from your herd which
should ensure that antibodies specific to the organisms found on the
farm are passed to calves.
Results of colostrum pasteurization research suggest that heat-treating
colostrum may present an excellent opportunity to reduce bacterial
populations in colostrum and increase IgG absorption, thereby reducing
the percentage of dairy calves that experience failure of passive
antibody transfer. The explanation of why IgG absorption is improved
when colostrum is pasteurized is not yet clear, although it may be due
to changes in colostrum components when they are exposed to heat or
possibly to reduced competition between proteins for absorption.
Past research has shown that bacteria introduced into the gut before
colostrum feeding can reduce the amount of IgG absorbed by calves. But,
in a recent Penn State study, calves fed colostrum that contained a high
bacterial load (measured by standard plate count and coliform count)
absorbed similar amounts of IgG as calves fed colostrum with a low
Although further research is needed to explain why IgG absorption
improves, it seems clear that heating colostrum does offer advantages in
providing cleaner colostrum for calves along with improved IgG
absorption. This could be particularly helpful in herds working to limit
the spread of Johne’s.