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1 September 2015 CRYOPRESERVATION OF ONAGER (EQUUS HEMIONUS ONAGER) EPIDIDYMAL SPERMATOZOA
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Abstract

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 HollowTubesTM), 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.

Copyright 2015 by American Association of Zoo Veterinarians
María Teresa Prieto Pablos, Joseph Saragusty, Julián Santiago-Moreno, Julia Stagegaard, Frank Göritz, Thomas Bernd Hildebrandt, and Robert Hermes "CRYOPRESERVATION OF ONAGER (EQUUS HEMIONUS ONAGER) EPIDIDYMAL SPERMATOZOA," Journal of Zoo and Wildlife Medicine 46(3), 517-525, (1 September 2015). https://doi.org/10.1638/2014-0243.1
Received: 15 December 2014; Published: 1 September 2015
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