Cryopreservation of Pig Semen Using a Quercetin-Supplemented Freezing Extender

Reactive oxygen species (ROS) produced during freeze-thaw procedures cause oxidative damage to the sperm, reducing fertility. We aimed to improve the post-thaw quality of pig sperm by quercetin (QRN) supplementation to reduce the cryodamage associated with the freeze-thaw procedure. Four equal aliquots of pooled boar semen were diluted with a freezing extender supplemented with different concentrations of QRN (0, 25, 50, and 100 mu M) and then were subjected to cryopreservation in liquid nitrogen. Semen analysis was performed following 7 days of cryopreservation. Results demonstrated that the semen samples supplemented with 50 mu M QRN significantly improved the post-thaw sperm quality than those subjected to other supplementations (p < 0.05). Semen samples supplemented with 50 mu M QRN showed significantly improved plasma membrane functional integrity (47.5 +/- 1.4 vs. 43.1 +/- 4.1, 45.3 +/- 1.7, and 44.1 +/- 1.4) and acrosome integrity (73.6 +/- 3.4 vs. 66.3 +/- 2.4, 66.7 +/- 3.6, and 68.3 +/- 32.9) as compared to the control, 25 mu M, and 100 mu M QRN groups, respectively. The mitochondrial activity of the 50 mu M QRN group was greater than control and 25 mu M QRN groups (43.0 +/- 1.0 vs. 39.1 +/- 0.9 and 41.9 +/- 1.0) but showed no difference with the 100 mu M QRN group. Moreover, the 50 mu M QRN group showed a higher sperm number displaced to 1 cm and 3 cm points in the artificial mucus than other groups. Therefore, supplementing the freezing extender with QRN can serve as an effective tool to reduce the magnitude of oxidative damage associated with sperm freezing.