Cholesterol-Loaded Cyclodextrin Addition to Skim Milk-Based Extender Enhances Donkey Semen Cooling and Fertility in Horse Mares.

The research article tests and compares the impacts of using a commercially available skim milk-based extender (SKM) and the same extender, but with added cholesterol-loaded cyclodextrin (SKM-CLC), on the quality and fertility of cooled donkey semen. The researchers found that including CLC in the SKM extender improved the ability to cool the semen and fertility rates when used to impregnate horse mares.

Experimental Design

• The study was conducted in two parts. In the first experiment, thirty-five ejaculates from seven jacks (male donkeys) were split into two groups: one using the SKM extender and the other using the SKM-CLC extender.
• The semen was diluted with the extender to 50 million sperm/mL and then chilled at 5°C for 48 hours.
• Semen was evaluated for various parameters before (0), 24 and 48 hours after cooling using Computer-Assisted Sperm Analysis (CASA) and flow cytometry.
• The parameters assessed included Total Motility (TM), Progressive Motility (PM), percentage of sperm with Rapid Motility (RAP), Plasma Membrane Stability (PMS), and High Mitochondrial Membrane Potential (HMP).
• In Experiment 2, the fertility effects of SKM and SKM-CLC were evaluated. Semen, extended in either SKM or SKM-CLC and cooled-stored for 24 hours, was used to inseminate 15 mares (female horses).
• Mares’ pregnancy was diagnosed 15 days post-ovulation and the conception rates were recorded.

Research Findings

• At the outset, no differences were observed in the assessed parameters of semen regardless of the extender used before cooling.
• However, over time, semen using the SKM-CLC extender showed better TM, PM, RAP, PMS, and HMP than semen using only the SKM extender at the 24-hour and 48-hour post-cooling marks.
• When it came to fertility rates, the mares that were inseminated with semen extended using SKM-CLC had a higher conception rate (47%, 7 out of 15 cycles) than those mares inseminated with SKM-extended semen (13%, 2 out of 15 cycles).

Conclusions

• The addition of cholesterol-loaded cyclodextrin (CLC) to the skim milk-based extender (SKM) improves the cooling ability of donkey semen and increases its fertility when used in horse mares.
• The researchers note that further research is needed to determine if similar improvements in fertility can be achieved with mares and jennies (female donkeys) in standard veterinary practices.