A comparison of time, temperature, and refreezing variables on frozen sperm motility recovery.

OBJECTIVE

To compare motility recovery among methods of thawing semen in serial freeze-thaw processes.

DESIGN

A comparison of treatments.

SETTING

Semen cryobank laboratory.

PARTICIPANTS

Semen samples from an existing cryobank.

INTERVENTIONS

Portions of each of 35 ejaculates were thawed serially in either a 37 degrees C water bath for 10 minutes or at room temperature for 30 minutes. Motility was estimated, and the samples were immediately refrozen. Thaws were performed initially (T1), at 24 hours (T2), and at 1 week (T3).

MAIN OUTCOME MEASURE

Percent motility.

RESULTS

The initial motility of all samples averaged 73.2%. Serial thaws at 37 degrees C yielded mean motility recoveries of 34.0%, 21.8%, and 8.3% for T1, T2, and T3, respectively. Those at room temperature were 22.4%, 7.9%, and 1.3%. Motilities progressively decreased from initial to final thaw regardless of temperature. Semen thawed at 37 degrees C had a higher motility recovery at all thaw times compared with samples thawed at room temperature.

CONCLUSIONS

For sperm frozen rapidly in liquid nitrogen and for sperm subjected to multiple freeze-thaw processes, motility recovery is improved if thaw is carried out at 37 degrees C versus room temperature.