Entrapped air volume and extender type influence boar semen quality during simulated transport

The presence of an air chamber in semen doses is believed to alter liquid dynamics during transport. This study aimed to evaluate how different air volumes are associated with changes in semen quality under transport simulation, using short- (SHORT) and long-term (LONG) extenders. Twenty ejaculates from boars (one per boar) were split, diluted in SHORT or LONG extenders, packaged into tubes sealed at different heights to obtain four amounts of air inside the doses (0%, 10%, 20%, and 40% air), and subjected to transport simulation for 6 h. Data were analyzed with repeated measures models, including air volume, extender type, storage time, and interactions as fixed effects. Logistic regression modeled progressive motility decline, and model-based dose-response curves were used to estimate air-volume limits associated with maintaining progressive motility ≥70%. Total and progressive motility decreased, and pH increased as the amount of air inside the doses increased (P < 0.01). After 30 min of the thermoresistant test, motility was reduced in semen doses with 40% air (P < 0.05). The group with 40% air had a lower proportion of cells with no apoptotic-like changes, reduced percentage of cells with high mitochondrial activity, and lower plasma and acrosomal membrane integrity than other groups (P < 0.05). Oxidative stress was higher in doses with 20% and 40% air compared to 0% and 10% (P < 0.05). Dose-response equations revealed that short-term extenders showed earlier and steeper declines for progressive motility. This study is the first to quantitatively model air-volume limits associated with progressive motility decline under vibration exposure. Reducing air during sealing may help preserve boar semen.