AETA Practice Tip

By Marianna Jahnke and Dr. Tyler Dohlman, College of Veterinary Medicine, Iowa State University

Who has not gotten frustrated with a straw exploding or issues with loading a direct transfer 0.25-cc straw? Last year we had some problems with the yellow 0.25-cc DT straws that are commercially sterilized and repackaged in groups. We had a few straws exploding, and within those straws we noticed that the cotton plugs and the PVC were separating during the loading process. As we were pulling the last column of ethylene glycol, the ethylene glycol kept going through the cotton plugs into the syringe as seen on the images. As we all have been trained and continue to train others, it is important to make sure fluid penetrates the PVC and cotton plugs in order to create a good seal to the straw. With this issue, our concerns were that the straws were not sealing properly, leaving them at an increased risk of exploding during the thawing process or even potentially allowing liquid nitrogen to enter the straw. This is probably not new information to some of you who have been in the industry for some time and it probably has been discussed over the years, but this was our first major straw issue. In addition, we have noticed other straws from other ET practitioners that seem to be doing the same thing, with a cotton plug being exposed at the end of the straw or gone completely.

To eliminate this issue, we ordered a different lot and brand of nonsterilized, bulk, yellow 0.25-cc DT straws, and they have not provided us with the same issue. So, we wonder whether the straws were faulty to begin with or whether the sterilization of the straws causes any type of damage to the PVC powder/cotton plug. Others whom we have communicated with said that storage humidity may play a role in it also. Since embryo transfer has many variables, this is just another one to add to the list. We have been salvaging these cryopreserved straws by removing the straw plug prior to submersion in a water bath in order to avoid the loss of an exploded straw, which is obviously not ideal. So to conclude, we recommend that all evaluate the end of the straws after loading to assure proper straw (PVC and cotton plug) function.

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