Semen cryopreservation in the Indian rhinoceros (Rhinoceros unicornis)

Abstract 

The objective was to identify an extender and cryoprotectant combination for Indian rhinoceros (Rhinoceros unicornis) sperm that yielded high post-thaw sperm quality. Male Indian rhinoceroses (n=6; 7.5–34 yr old) were anesthetized and subjected to a regimented electroejaculation procedure (75–100 mAmps; 4–10 volts; 7–150 stimuli; total of 10 electroejaculation procedures). High quality semen fractions from each ejaculate were divided into four aliquots and a 2 x 2 factorial design used to compare the effect of two sperm extenders (standard equine [EQ] and skim milk-egg-yolk-sugar [SMEY]), and two cryoprotectants (glycerol and dimethylsulfoxide [DMSO]). Cyropreserved samples were thawed and assessed for motility, viability and acrosome integrity over time. Electroejaculate fractions processed for cryopreservation had high sperm concentration (516×10⁶/mL) and motility (79%). Post-thaw sperm characteristics were higher (P<0.05) when semen was cryopreserved in EQ versus SMEY. Post-thaw motility of sperm cyropreserved in EQ averaged 50–55% compared to 22–37% in SMEY, with no significant differences in sperm characteristics of samples cyropreserved in glycerol and DMSO. In conclusion, sperm collected from Indian rhinoceroses via electroejaculation were cryopreserved using EQ extender with either glycerol or DMSO; post-thaw quality was adequate for use in assisted reproductive procedures.

Keywords: Indian rhinoceros, Sperm cryopreservation, Spermatozoa, Semen, Testosterone