Development of assisted reproductive technologies in okapi (Okapia johnstoni) could contribute to increasing genetic diversity in the captive population. The aim of this study was to evaluate the use of two common cryoprotectant agents (CPAs), glycerol (Sigma Chemical Co., St Louis, MO) and dimethyl sulfoxide (Sigma Chemical Co., St Louis, MO), at concentrations of 1%, 2%, and 4%, to determine the optimal freezing conditions for okapi semen. Samples were assessed for motility and progressive status at the following stages: at initial collection, addition of extender, cooling to 4°C, and post thaw. Prior to freezing both cryoprotectants appeared to have similar motility and forward progressive status ranging from 15–35%, average 26% with a forward status of 3.0/5. When comparing post-freezing samples the 4% glycerol dilution demonstrated the greatest post-thaw motility of 18% and forward progressive status of 3.4/5, when compared to 3–14% motility and 1.6–2.5/5 progressive forward motility in other samples. To the author’s knowledge this is the first report of cryopreservation of okapi semen.
The authors would like to thank Dr. Scott Citino and the White Oak Conservation Center staff for their assistance in collecting these samples.