Sperm sex-sorting in the Asian elephant (Elephas maximus)

In captive Asian elephants, there is a strong need for production of female offspring to enhance reproduction, counter premature aging processes in female animals and reduce challenging management situations derived from husbandry of several bulls in one institution. Artificial insemination of flow cytometrically sex-sorted spermatozoa offers the possibility to predetermine the sex of offspring with high accuracy. The aims of this study were to determine a suitable semen extender and basic parameters for flow cytometrical sex-sorting of Asian elephant spermatozoa. In total 18 semen samples were collected by manual rectal stimulation from one bull. Sperm quality parameters and sex sortability of spermatozoa were evaluated after dilution in three semen extenders (MES-HEPES-skim milk, MES-HEPES, TRIS–citric acid) and DNA staining. MES-HEPES-skim milk was the only semen extender found suitable to sex Asian elephant spermatozoa. From 18 ejaculates collected, 12 were successfully sorted with a purity of 94.5 ± 0.7% at an average sort rate of 1945.5 ± 187.5 spermatozoa per second. Sperm integrity, progressive and total motility were 42.6 ± 3.9%, 48.1 ± 3.3%, 59.4 ± 3.8% after DNA labelling, and 64.8 ± 3.2%, 58.0 ± 5.0%, 70.8 ± 4.4% after sorting, respectively. After liquid storage of sorted spermatozoa for 12 h at 4 °C, sperm integrity, progressive and total motility were 46.4 ± 5.2%, 32.2 ± 4.2% and 58.2 ± 3.9%, respectively. The obtained results provide a promising base to inseminate Asian elephants with sexed semen.