 groups were considered in the results.
In this study, three different patterns of response were observed on males throughout the cryopreservation process (Figure 1). From the 38 males used in this study, 44.7% showed the response pattern 1, 26.3% showed the response pattern 2, and 28.9% showed the response pattern 3. Sperm head dimensions among ejaculates were quite similar for each male with coefficients of variation within a male (between ejaculates) lower than 10 (ranging from 1.14 to 9.30) for all the sperm head parameters. Males always showed the same pattern of response to cryopreservation regardless of the ejaculate.
Data plotted correspond to three males, each one showing a different response pattern. p2a: perimeter to area (Perimeter2/4·π·Area).
The males grouped under the “response pattern 1” showed no significant changes in their sperm head dimensions during cryopreservation (Table 1). Changes on sperm dimension were close to 0 and quite similar between stages of the crypreservation process.
The males characterized as “response pattern 2” showed a progressive decrease in their sperm head dimensions throughout the cryopreservation process. Changes in sperm head dimensions from fresh to prefreezed and from prefreezed to thawed semen were quite similar, being the change from fresh to thawed semen the highest (Table 1). This did not apply to the p2a (perimeter to area) shape factor because in the transition from fresh to prefreezed stage there was an increase (prefreezing) and then decrease (postthawing) to levels below those observed in fresh semen.
Finally, males belonging to the “response pattern 3” showed an important decrease of their sperm head dimension from fresh to prefreezed semen, with minimal changes at thawing (Table 1). For these males, total changes on sperm head dimensions took place mainly during the prefreezing stage and these changes were close to 0 from prefreeze to thawing. As for males with response pattern 2, sperm head p2a initially increase on average and then decrease at thawing.
Differences on sperm quality throughout the cryopreservation process between response patterns are presented on Table 2. In fresh and prefreezed semen, the three patterns showed a quite similar sperm quality. Only sperm from males with the response pattern 3 showed a significant higher viability and percentage of sperm motility. After thawing, sperm quality of males with the response pattern 2 decreased considerably, being the lowest. Males with the response pattern 3 showed the best sperm quality, while those males with the response pattern 1 showed an intermediate sperm quality. When we examined the ratio of change compared to the values in fresh semen (normalized percentages), the same results were observed but with some differences. In this case, the three groups showed a similar decrease in quality during the prefreezing stage, and no differences were observed in the change of the quality of sperm movement among groups. Males showing the response pattern 2 again showed a greater decline in sperm quality.
We also examined the additive relationships of each male with the other males showing the same response pattern and with those showing different pattern. The within additive relationship coefficients were twice large as that seen between coefficients among groups of response patterns (Table 3). Thus, males who share the same pattern of response were found to be more closely related to each other than with those showing different responses.
The present study has revealed the existence of three distinct patterns of response, based on changes that occur in the dimensions of the sperm head during the cryopreservation process, and how the sperm quality on thawed semen varies depending on these patterns.
The study has been designed to disentangle male effects from other environmental or management effects. Thus, our experimental design was aimed at standardizing the semen collection, as a way to assure that differences in the response to cryopreservation were due to male-specific factors rather than external fact