The Paradoxical Relationship Between Stallion Fertility and Oxidative Stress

ABSTRACT The relationship between stallion fertility and oxidative stress remains poorly understood. The purpose of this study was to identify criteria for thoroughbred fertility assessment by performing a logistical regression analysis using “dismount” sperm parameters as predictors and weekly per-cycle conception rate as the dependent variable. Paradoxically, positive relationships between fertility and oxidative stress were revealed, such that samples that produced pregnancies exhibited higher rates of 8-hydroxy-2′-deoxyguanosine release (1490.2% vs. 705.5 pg/ml/24 h) and lower vitality (60.5% vs. 69.6%) and acrosome integrity (40.2% vs. 50.1%) than those that did not. We hypothesized that the most fertile spermatozoa exhibited the highest levels of oxidative phosphorylation (OXPHOS), with oxidative stress simply being a by-product of intense mitochondrial activity. Accordingly, an experiment to investigate the relationship between oxidative stress and motility was conducted and revealed positive corre...