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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. BACK |