Submitted to: Cryobiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/5/2008
Publication Date: N/A
Interpretive Summary: We have used a comparative approach to understand the physiology of sperm survival after cryopreservation. In general, crane sperm survive the freeze/thaw process relatively well, and produce 50-90% fertile eggs after artificial insemination with thawed semen. Conversely, the fertilizing of frozen/thawed turkey sperm is severely compromised after cryopreservation. As a continuation of ongoing comparative research, our objective here was to evaluate the impact of different cooling and thawing rates on the cryosurvival of turkey and crane sperm. We tested rapid, moderate and slow cooling rates, as well as moderate and slow thawing rates. Moderate and slow cooling rates were remarkably superior in preserving sperm viability for both species when compared to rapid cooling; however, slow thawing did not improve viability for either species included in this study. These data are important for developing effective semen cryopreservation protocols for avian species.
Technical Abstract: A comparative approach (Sandhill crane (Grus canadensis, n = 13); domestic white turkey (Meleagridis gallopavo n = 40) was used to determine the possible benefits of the addition of different compounds and variation in cooling and thawing rates, and volume of semen. Sperm was frozen in cryovials using a range of dimethylacetamide (DMA) concentrations from 6-30%. Experiments evaluated the efficacy of (1) rapid, moderate and slow cooling rates, (2) moderate and slow thawing rates, and (3) variation in the final volume of semen frozen. Sperm viability was assessed using the eosin-nigrosin stain. Moderate and slow cooling rates were remarkably superior (p<0.05) in preserving sperm viability in both species when compared to rapid cooling. However, slow thawing did not improve (p>0.05) viability for either species included in this study. Increasing the final volume of crane semen from 20 ul to 120 ul yielded slightly higher viability after thawing that averaged 6% and 3.1% in samples with and without 5% sucrose respectively. For both the turkey and the crane, higher DMA concentrations (24-30%) improved the viability of samples post-thaw, when higher DMA concentrations were used. Results demonstrate specific differences in sperm survival after freezing and thawing in response to the addition of cryoprotectants. These data further emphasize the need for species specific studies to optimize crypopreservation protocols; in particular, evaluation of cooling rates is important for sperm survival.