Chilling Colostrum
One way to reduce the bacteria load in colostrum headed for the refrigerator or freezer is to chill it down to around 60F (16C) before it is stored.
A preview of the practical fact sheet on the WHY and HOW appears below. Sorry, but no pictures - you will have to wait until this is posted online at www.calffacts.com later this year
Colostrum
Chilling
- ·
Chill colostrum
quickly if it is to be stored.
- ·
Water-bath
method
- ·
Ice-immersion
method
In the first place, if we are going to
feed colostrum within thirty minutes after it is collected, why would we want
to chill it? Obviously, the answer is
that it does not need chilling. Just feed it promptly.
Why
chilling?
We want to feed clean colostrum. Our
goal is to reduce the bacterial load in colostrum in order to promote good gut
health. Clearly it makes sense to
avoid bacterial inoculation of colostrum as a first step toward this goal. That means clean teats in the parlor. In
addition, we need to start with clean collection, feeding and storage
equipment.
In many cases not all our colostrum is
going to be fed directly from the dam. If
it is going to be held more than one-half hour until it is fed the colostrum is
at risk of growing bacteria.
Why
chill quickly?
Colostrum is very good bacterial growth
medium – favorable pH and lots of readily available nutrients. Also, when
collected from a cow it is at an excellent temperature to encourage bacterial
growth.
By the way, we describe these growth rates using the term
“Generation Time.”
At cow body temperature the generation
time for coliform bacteria is about twenty minutes. Yes, that is correct. These
bacteria can double in numbers in twenty minutes. That means in less than three
hours after collection warm colostrum with an initial bacteria count of only
1,000cfu/ml (cfu/ml=colony forming units per milliliter) can have a terminal
bacteria count of around 130,000cfu/ml! That is high enough to make a calf very
sick.
One cost effective way to slow down the
rate at which bacteria multiply is to lower the temperature of the growth
medium – colostrum. For example, when we reduce colostrum temperature from 95
to 60 degrees (35C to 16C), coliform generation times increase from roughly
twenty to one hundred and fifty minutes. Thus, if we want to cut down bacteria
numbers that come from initial inoculation one alternative is to rapid chill
the colostrum to at least 60 degrees. Then, when it is put into either a
refrigerator or freezer the unit has plenty of time to do the rest of the
chilling without the risk of excessive bacteria growth.
Farm-friendly
ways to Chill: Water-bath method
In order to be “farm-friendly” a
chilling method has to be simple and cost effective.
One such method is a water bath.
Colostrum is transferred into containers smaller than milker pails or
five-gallon pails. Most folks use calf nursing bottles. Others buy two or four
quart plastic containers. Unless the containers are one-use disposable ones
make sure that it is easy to brush all the inside surfaces.
Right-size the tub for the water bath
based on your experience with colostrum volume. Larger farms may consider using
several water bath containers for increased flexibility. Remember that for most
efficient heat transfer at least ¾ of the container holding the colostrum needs
to be submersed in the ice-cold water.
And, avoid packing ice around the
containers without water. This is not an efficient method of chilling because
the ice water is needed to promote effective heat transfer.
See picture below
of a plastic water bath with nursing bottles. This farm purchased plastic tubs
that fit inside their refrigerator to promote even better chilling. [Including
what appears to be a workers lunch!]
Also, remember to close off the opening at the top of these containers.
Note in the picture below the dairy chose to snap nitrile gloves onto the
nursing bottles [by the way, at this dairy blue gloves indicated high quality
colostrum and white glove indicated low quality colostrum.].
[NO PICTURE]
Source of ice? Large operations should consider purchasing a
used restaurant ice maker. Smaller dairies find it practical to use the freezer
compartments of refrigerators or a small chest freezer for making ice. One
dairy cuts the bottoms off of one-gallon plastic jugs to create big oversize
hockey pucks of ice. Several of my clients repeatedly freeze “cold-packs”
rather than use water for making ice.
Farm-friendly
ways to Chill: Ice-immersion method
A second “farm-friendly” method is adding containers of
ice directly to the warm colostrum. An ice:colostrum ratio that works well to
chill just-collected colostrum to 60 degrees within one-half hour is 1 quart of
ice to 1 gallon of colostrum (1 liter of ice to 4 liters colostrum).
In general multiple small ice containers
will do a quicker job of chilling compared to one larger container. For
example, six 16 ounce recycled plastic soft drink bottles compared to one
one-gallon plastic jug.
See the picture below of a gallon jug of ice in a
bucket containing about three gallons of colostrum. I took this bucket out of
the refrigerator and removed the lid to take this picture. It is a good idea to
cover containers of colostrum in refrigerators to reduce the thickness of the
dry scum (mostly milk fat) that forms during storage.
[NO PICTURE]
A few dairies place the equivalent of 3
quarts of ice in the stainless steel milker bucket before milking the fresh
cow. This procedure eliminates errors in remembering to add ice once the fresh
cow is milked.
As shown above other dairies with more
than a few quarts of colostrum to chill pour 3 gallons of colostrum into a
five-gallon pail, add a one-gallon jug of ice, put a lid on the pail and put
the entire pail-jug-colostrum into a refrigerator. The colostrum chills from
the inside-out as well as from the outside-in.
One caution! When containers are placed
directly into colostrum they need to have as few bacteria on their surfaces as
is practical. Rinsing them quickly with tap water as they are transferred from
the freezer into the colostrum is a best management practice.
If these
containers are used more than once someone needs to be given the responsibility
of cleaning these each time they are cycled through the freezer. Also, the
person cleaning the bottles needs to remember to avoid bacteria build-up
underneath the caps where screw onto the bottles and jugs.
Extended
cooling may be desired
Many dairies have one person responsible
for handling colostrum. In order to both rapidly chill colostrum and keep it
cold until that person is available some farms extend chilling.
For example, after placing ice
containers directly into colostrum for initial chilling the night shift workers
simply replace the first batch of ice bottles with a fresh set as they leave.
Or, additional ice is added to the ice bath to carry the colostrum over until
the colostrum person is available.
If an ice bath container is right-sized to
fit into a refrigerator that solves the cooling problem. Another dairy
immediately after harvesting colostrum places a one-gallon jug of ice in each stainless
steel milker bucket and they go into a chest freezer to wait for
processing.
