Post-coital sperm recovery and cryopreservation in the Sumatran rhinoceros(Dicerorhinus sumatrensis) and application to gamete rescue in the Africanblack rhinoceros (Diceros bicornis)

Sumatran rhinoceros (Dicerorhinus sumatrensis) sperm samples were collected from a postcopulatory female and characterized to determine their potentia l for sperm preservation and future use in artificial insemination. Five sa mples of acceptable quality from one male were used to compare the effect o f two cryoprotectants (glycerol and dimethyl sulfoxide (DMSO)) and two post -thaw protocols (untreated and glass wool column) on sperm quality. The per centage of motile spermatozoa, sperm motility index (0-100) and sperm morph ology were evaluated subjectively, and viability and acrosomal status were assessed using fluorescent markers. Evaluations of frozen-thawed spermatozo a were performed over a 6h incubation interval. Post-coital semen samples n = 5; 104.0 +/- 9.1 ml; 2.5 +/- 0.8 x 10(9) total spermatozoa; mean +/- SEM ) exhibited a sperm motility index of 56.7 +/- 3.3, and contained 40.2 +/- 6.3%, 72.0 +/- 3.2% and 79.8 +/- 6.5% normal, viable and acrosome-intact sp ermatozoa, respectively. Glycerol and DMSO were equally effective as cryopr otectants and, regardless of post-thaw protocol, samples retained greater t han 80% of all pre-freeze characteristic values. Processing semen samples t hrough glass wool yielded higher quality samples, but only half the total n umber of motile spermatozoa compared with untreated samples. High values fo r pre-freeze sperm characteristics were also maintained after cryopreservat ion of epididymal spermatozoa from one black rhinoceros (Diceros bicornis) using the same protocol. In summary, Sumatran rhinoceros spermatozoa of mod erate quality can be collected from post-copulatory females. Rhinoceros spe rm samples show only slight reductions in quality after cryopreservation an d thawing and have potential for use in artificial insemination.