When shipping semen in the winter, there is often a risk of cold shock causing irreversible damage to the cells . Due to the variability in shipping conditions it is difficult to ensure that the dose temperature stays in an acceptable range. This situation is often encountered in colder climates and decision-making can be difficult given the potential financial loss. With semen being sensitive to rapid cooling and warming , gradual warming after an extended exposure to cold temperatures could potentially limit damage to the cells as well as limit financial repercussions.
The first aim of this study was to identify at what day the effects of cold shock appear in motility, progressivity and agglutination to know until which day the doses could be used. The second aim was to determine if the warming technique to 17°C can influence motility, progressivity and agglutination.
Ejaculates were collected from 10 commercial boars, extended in Preserv® Xtreme (GenePro Inc.), a 7-day culture medium, at a concentration of 40M/mL and packaged single sire in 75 mL bags. Samples were stored in Styrofoam boxes and exposed to 5°C or 10°C for 12 or 24 hours. Conditions were chosen to simulate overnight shipments in the winter. After the cold shock, the doses were stored at 17 °C. Two warmup methods were used: storage in S.S.U. directly at 17 °C or left in the Styrofoam box in the S.S.U. Temperatures were monitored during cold shock and warming. A total of 8 conditions and a control were evaluated daily on motility, progressivity and agglutination, between day+2 and day+7 with a CASA (Computer-assisted sperm analysis) system (ISAS V1, Proiser). Data were analysed by ANOVA on a linear mixed model.
The interaction plots show that the cold shock effects on motility are visible on day 2 (control mean: 88.2, subject mean: 73.8, p < 0.0003; wilcoxon rank test). As expected, samples stored at 10 °C had higher sperm motilities than samples stored at 5 °C, whatever the day (mean 5 °C: 67.9, mean 10 °C: 76, p < 8.8e-13). Although progressivity was lower in samples stored in colder conditions (mean 5 °C: 41.2, mean 10 °C: 42.9, p < 3.492e-09), the curve and the peak were similar across all samples. Surprisingly, a fast warmup seemed to be more favorable to the sperm than a slow warmup (p < 0.03 for progressivity, p < 0.02 for motility).
These results will give sow farms better knowledge and understanding of cold shock, thus helping them make decisions when receiving doses at a low temperature.