Effect of novel lyophilized extenders on stallion post-thaw sperm motility.

Overview

• This study evaluated the effectiveness of new lyophilized (freeze-dried) extenders, which can be stored at room temperature, on the motility of stallion sperm after thawing.
• The research compared two commercial extenders and two novel lyophilized extenders using different cryopreservation protocols to determine their impact on post-thaw sperm movement.

Background and Purpose

• Freezing extenders are substances used in the cryopreservation process to protect sperm cells during freezing and thawing.
• Typically, these extenders require refrigeration or freezing for storage, which poses logistical challenges for storage and distribution.
• Lyophilization (freeze-drying) allows extenders to be stored at room temperature, potentially simplifying storage and transport.
• The study aimed to assess whether these novel lyophilized extenders could maintain or improve sperm motility after thawing compared to standard commercial extenders.

Methods

• Samples: Ejaculates were collected from 28 different stallions to provide a diverse sample population.
• Extenders tested:
  • Two commercial freezing extenders commonly used worldwide.
  • Two novel lyophilized extenders, named STAR and MX3.
• Cryopreservation Protocols:
  • CP1: Equilibration period of 20 minutes before freezing.
  • CP2: Equilibration period of 60 minutes before freezing.
• After thawing, total motility (TM) of sperm was measured to assess sperm viability and quality.

Results

• There were no significant differences in total motility between the two cryopreservation protocols (CP1 and CP2) within each extender type, indicating that equilibration length did not have a major impact on motility.
• The STAR lyophilized extender produced significantly higher total motility than the Botucrio commercial extender (P < 0.05).
• No significant differences in total motility were observed between other extenders (including MX3 and the other commercial extender).
• Among all samples evaluated, 20 ejaculates showed peak total motility when frozen with the lyophilized extenders combined with the CP1 protocol.

Conclusions

• Lyophilized extenders, especially STAR, are promising alternatives to traditional commercial extenders for stallion sperm cryopreservation.
• These extenders offer practical benefits by being storable and distributable at room temperature for at least one year, facilitating easier handling and logistics.
• Using lyophilized extenders with a shorter equilibration period (20 minutes) may optimize post-thaw sperm motility in many cases.

Significance and Implications

• This research supports the development of storage-stable freezing extenders that do not require cold storage, which can benefit equine breeding programs by reducing costs and increasing convenience.
• Higher sperm motility after thaw increases the chance of successful artificial insemination and fertility in stallions, impacting breeding efficiency.
• Future studies could explore additional performance parameters such as sperm viability, DNA integrity, and fertility outcomes using these lyophilized extenders.