Comparison of various extenders for freeze-preservation of semen from selective captive wild ungulates

Semen collected by electroejaculation from selected captive wild ungulates was used to evaluate the cryoprotective ability of 4 semen diluents. Three species of ungulates were used: blesbok (Damaliscus dorcas phillipsi), dorcas gazelle (Gazella dorcas), and onager (Equus hemionus onager). Fresh semen was immediately evaluated for the percentage of motility and the progressive motility, and an aliquot was fixed for evaluation of the acrosomal integrity of spermatozoa. The remaining volume of ejaculate was divided into equal aliquots and either frozen raw on dry ice or extended with each of the 4 diluents. Samples were concurrently equilibrated at 5 C, frozen on dry ice, and stored in liquid nitrogen. Aliquots were thawed for evaluation of motility traits and spermatozoal acrosomes. Each diluent provided cryoprotection in each species. However, spermatozoa varied in ability to survive cryopreservation, and postthaw viability was influenced by the semen diluent used. Although ineffective in the onager, the study of morphologic forms of spermatozoal acrosomes proved useful for assessing the cryoprotective property of semen diluents in the blesbok and dorcas gazelle.