The Effect of Low Oxygen During the Early Phases of Sperm Freezing in Stallions With Low Progressive Motility: Can We Improve Post-Thaw Motility of Stallion Sperm?

The objective of this study was to determine the effectiveness of oxygen removal in minimizing oxidative stress to improve fertile longevity of equine spermatozoa. Stallion ejaculates (n = 6) were treated with increasing doses of the oxygen scavenger Oxyrase (0.6 U/mL, 1.2 U/mL, 2.4 U/mL, and 5.0 U/mL). Samples were cryopreserved, thawed, and analyzed for motility over 24 hours at ambient temperature. These data suggest a role of excessive oxygen in the reduced motility of cryopreserved samples as 2.4 U/mL Oxyrase minimized the loss of post-thaw motility over the other doses and control treatments. Oxygen, a key component of reactive oxygen species generation, is directly involved in oxidative damage, and its removal may trigger metabolic changes that are more suited for post-thaw motility maintenance. Removal of oxygen from semen before cryopreservation may promote increased post-thaw fertility and may have the potential to overcome stallion variability in cryosurvival.