CRYOPRESERVATION OF ONAGER (EQUUS HEMIONUS ONAGER) EPIDIDYMAL SPERMATOZOA.
Genetic diversity is a primary component of adaptive evolution, and its loss or reduction can decrease the long-term survival probability of populations. Utilization of cryopreserved semen may be considered a perfect tool to improve genetic diversity, reduce inbreeding, and avoid animal translocation for breeding. The present study aimed at finding a reliable epididymal sperm freezing protocol for the critically endangered onager (Equus hemionus onager). Six testicles from three animals were processed postmortem. The effects of two transportation temperatures (22°C and 4°C; testicles submerged in saline), two cryopreservation techniques (conventional liquid nitrogen vapor freezing in straws and directional freezing in 8-ml HollowTubes(TM)), and two postthaw incubation temperatures (22°C and 37°C; evaluated after 0.5, 1, 2, and 3 hr) were tested in a 2×2×2 experimental design. Sperm samples were evaluated for motility, viability, acrosome integrity, and sperm morphology. The resulting optimal freezing protocol includes transportation of testicles at 4°C, cryopreservation by directional freezing, and, if needed, postthaw incubation at 22°C. With this combination of transportation temperature and cryopreservation technique, the authors obtained the following postthaw values normalized to prefreezing values: 60.3±8.8% motility, 60.7±13.3% viability, 75.3±9.5% acrosome integrity, and 94.7±2.9% normal morphology (excluding defects due to the epididymal origin of the sperm). After incubation at 22°C, motility values for the above combination were 40±5.7%, 30.3±5.2%, 28.3±4.4%, and 16.7±4.4% for 0.5, 1, 2, and 3 hr, respectively. In conclusion, with this protocol, good quality semen can be stored for future use in artificial inseminations when and where needed.
María Teresa Prieto
MT
Pablos
Joseph
J
Saragusty
Julián
J
Santiago-Moreno
Julia
J
Stagegaard
Frank
F
Göritz
Thomas Bernd
TB
Hildebrandt
Robert
R
Hermes
D000818:Animals; D015925:Cryopreservation / Q000379:methods / Q000662:veterinary*; D004822:Epididymis / Q000166:cytology*; D018397:Equidae / Q000502:physiology*; D008297:Male; D012662:Semen Preservation / Q000379:methods / Q000662:veterinary*; D013081:Sperm Motility; D013094:Spermatozoa / Q000166:cytology* / Q000502:physiology*; D013696:Temperature
Assisted reproductive technologies; Equidae; Equus hemionus; directional freezing; epididymis; spermatozoa.