A simple, field-friendly technique for cryopreserving semen from Asian elephants (Elephas maximus)

- An equitainer will effectively cool Asian elephant semen without damaging it.
- Manual seeding does not improve post-thaw sperm quality.
- A dry shipper can be used as a cost-effective tool to cryopreserve Asian elephant semen.
- Thawing Asian elephant semen at high temperatures increases post-thaw motility.
- This method can be applied in zoo or field settings to bank Asian elephant semen.

The specific objectives of the present study were to investigate the effects of manual seeding, differing freeze and thaw rates as well as storage for 24 h at 4 °C prior to cryopreservation on post-thaw sperm quality in Asian elephants. Extended semen was cooled in an equitainer to 4 °C, frozen in liquid nitrogen vapour at various rates with and without manual seeding or in a dry shipper and thawed at 37, 50 and 75 °C. There was a significant effect of freeze rate on post-thaw motility (P < 0.0001) and acrosomal integrity (P < 0.005). The faster freeze rates in the dry shipper and at 1 cm or 2 cm above liquid nitrogen consistently provided better cryopreservation than slower freezing rates. Thaw temperature had no effect on post-thaw semen quality but there was an interaction between freeze and thaw rates with higher thaw rates resulting in superior post-thaw semen quality in straws frozen at fast rates. Storage of samples prior to freezing had a detrimental effect on post-thaw semen quality. In summary, our results indicate cooling extended semen in an equitainer and cryopreserving it by placing straws directly in a dry shipper is a simple technique for effectively cryopreserving Asian elephant semen in the field or zoo.