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Efficiency Of The BOVet Creations Embryo
Freezers
Joseph
M. Wright, D.V.M.
Genetics
Management Services
Castrovile,
Texas
The
Bovet Creations freezers are aluminum blocks with an
aluminum stem with several evenly spaced holes to
allow controlled lowering of the block into the neck
of a liquid nitrogen (LN2)tank. A rod is passed
through the holes to suspend the block in the neck of
the LN2 tank. The embryos are frozen in straws
that are placed in vertical holed drilled into the
block. I prefer to fill the holes with alcohol.
Aluminum,
an excellent conductor, allows for rapid cooling of
the block and provides a relatively uniform
temperature of the block.
Dr.
Walter North of Bovet Creations developed a
Stabilizer to fit over the neck of the tank.
His original purpose was to develop a means where the
desired seeding temperature could be maintained
indefinitely. The stabilizer is an aluminum
plate with numerous threaded holes where screws can
be used to level, secure and raise the level uniformly
at minute increments if desired.
There
are also 4 grooves, each on increasing in depth so
that each groove allows one to lower the freezer the equivalent
of 1/4 the depth of a hole in the stem of the
freezer. The stabilizer allows for excellent
control of the temperature of the freezer
block. I always leave the stabilizer on the
tank throughout the entire freezing procedure.
To
control the freezing rate of the freezer, one monitors
the cooling rate and increases the rate by lowering
the block deeper into the tank as required. The
type of LN2 tank makes a lot of difference in the
freezing rate. The level of Liquid Nitrogen in
the tank usually is important.
The
freezer, along with an LN2 tank, is an economical
unit. This makes an ideal freezing unit for a
practitioner freezing only a few embryos each
year. It is also an excellent back-up unit for
another freezer in case of break-down or power
outage. In addition, many of us like it as our
primary freezer.
The
charts that follow contain results after testing the
Bovet creations freezer many different ways. these
charts illustrate the efficiency of the freezer.
Joseph
M. Wright, D.V.M.
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