Liposome‑based extender consistently improves post-thaw semen quality in rams

Area of Science:

• Reproductive Biology
• Animal Science
• Cryobiology

Background:

• Cryopreservation of ram spermatozoa is vital for genetic improvement and conservation.
• Conventional egg-yolk-based (EY) extenders present challenges due to biological variability and biosecurity risks.
• Development of chemically defined alternatives is needed to overcome limitations of EY extenders.

Purpose of the Study:

• To compare the efficacy of a commercial liposome-based (LB) extender against a traditional EY extender for ram semen cryopreservation.
• To evaluate the impact of LB extenders on various in vitro sperm quality parameters post-thaw.

Main Methods:

• A split-ejaculate design was employed across two experiments involving 42 ejaculates.
• Ram semen was cryopreserved using either LB (OptiXcell®) or EY extenders.
• Post-thaw sperm quality was assessed using computer-assisted sperm analysis (CASA), flow cytometry (plasma membrane integrity, acrosome integrity, mitochondrial membrane potential), and the hypo-osmotic swelling test (HOST).

Main Results:

• LB-cryopreserved semen demonstrated significantly higher total and progressive motility, along with improved velocity parameters.
• A greater proportion of spermatozoa exhibited intact plasma membranes and preserved acrosomes when using LB extenders.
• Mitochondrial membrane potential was higher with LB in one experiment, indicating context-dependent effects; HOST showed no significant difference.

Conclusions:

• Chemically defined liposome-based extenders enhance multiple in vitro indicators of ram sperm function post-cryopreservation.
• LB extenders offer a promising alternative to conventional EY extenders, improving sperm quality parameters.
• Further in vivo fertility trials are necessary to confirm the reproductive efficacy of LB extenders in ram semen.