Salvaging urospermic ejaculates from brown bear (Ursus arctos)

Area of Science:

• Reproductive biology
• Cryopreservation science
• Animal reproduction

Background:

• Urine contamination in ejaculates causes osmotic stress, negatively impacting sperm quality.
• Effective sperm preparation techniques are crucial for successful artificial insemination and cryopreservation.

Purpose of the Study:

• To evaluate pre-freezing washing and density gradient centrifugation for reversing osmotic stress in urine-contaminated bear ejaculates.
• To determine the impact of these methods on sperm motility, viability, and acrosomal status before and after cryopreservation.

Main Methods:

• Experiment 1: Sperm washing with varying osmolality extenders (200-700 mOsm/kg) and centrifugation.
• Experiment 2: Density gradient centrifugation (PureSperm) and centrifugation control.
• Sperm analysis included motility, viability (SYBR-14/PI), and acrosomal status (PNA-FITC/PI) pre- and post-freezing.

Main Results:

• Pre-freezing washing, except at 700 mOsm/kg, showed no significant improvement in sperm viability compared to controls.
• Washing with 700 mOsm/kg solutions had detrimental effects on sperm viability.
• Density gradient centrifugation significantly improved pre-freezing sperm motility and viability.
• Sperm processed via density gradient centrifugation exhibited better cryopreservation capacity.

Conclusions:

• Density gradient centrifugation is a superior method for preparing urine-contaminated ejaculates for cryopreservation.
• Pre-freezing washing is not effective in mitigating osmotic stress in these samples.
• Optimized sperm preparation is vital for preserving reproductive potential in challenging samples.