Abstract

Male infertility and absence of males in a facility are contributing factors to the limited reproduction of Asian elephants in captivity. Subsequent transport for breeding purposes increases social stress, risks of disease transmission and management costs. Recent success in artificial insemination eliminated these obstacles only transporting the semen. However, the transport of fresh semen involves logistic difficulties: access to semen donors, consistent semen quality and preservation of the spermatozoa during transport. The use of cryopreserved sperm for artificial insemination (AI) can partially overcome these problems and can additionally be used for the establishment of genome resource banks. However, to date, attempts to cryopreserve Asian elephant spermatozoa have failed due to its sensitivity to freezing. Aims of this study were to identify the temperature range during which spermatozoa are most sensitive to chilling injury, and to use directional freezing (DF) to reduce cell damage during the freezing process. Semen was collected from two Asian elephants by manual stimulation, and DF was used for freezing sperm samples. In contrast to conventional freezing methods, DF facilitated a fast cooling rate, controlled ice crystal formation and cryopreservation of large volumes. Samples extended with a variety of DMSO extenders showed post thaw motility of 30–40%. DF was able to cryopreserve Asian elephant spermatozoa for the first time. As DF seems to reduce cryoinjury, it may become of interest to optimize existing cryopreservation protocols of other endangered species, or to make cryopreservation even possible in species with cryosensitive spermatozoa.