Protocol to preserve mouse freeze-dried spermatozoa in the thin plastic sheets

The preservation of mammalian freeze-dried (FD) spermatozoa is commonly performed using small glass ampules; however, they are bulky and breakable. In this study, we present a protocol to prepare and preserve mouse FD sperm using thin plastic sheets. This approach allows storing thousands of mouse strains in a card folder. We can also send the FD sperm domestically using a postcard without any extra equipment. For complete details on the use and execution of this protocol, please refer to Ito et al. (2021).