Post-Ejaculatory Blood Plasma Canine Prostate-Specific Esterase Concentrations May Predict Total Motility Decline After Sperm Freezing in Dogs

Despite the widespread use of cryopreserved dog semen, reliable predictors of individual semen freezability are still not available. This study investigated the relationship between post-ejaculatory blood plasma concentrations of canine prostate-specific esterase (CPSE) and semen quality following cryopreservation. The CPSE levels were quantified using a canine-specific sandwich-type immunoassay, and sperm quality was evaluated in fresh and frozen–thawed samples using motility, kinematic, and morphological sperm parameters. Cryopreservation resulted in a significant decline in sperm motility and morphology, with marked variability in the magnitude of post-thaw changes among individuals. CPSE showed significant correlations with several morpho-functional parameters in both fresh and frozen–thawed sperm (p ≤ 0.05). However, its strongest predictive value for freezability was observed for total motility (p = 0.004), with a minimum threshold of 53 ng/mL identifying dogs showing a ≥20% post-thaw motility decline (AUC = 0.785, p = 0.010). These findings suggest that post-ejaculatory CPSE levels in blood plasma may reflect sperm cryoresilience and serve as a potential biomarker of canine sperm freezability.