Association of Blood Plasma Vascular Endothelial Growth Factor and Testicular Artery Doppler Parameters with Canine Sperm Freezability

Semen cryopreservation is widely used in canine breeding, but individual variation in post-thaw semen quality limits its efficiency. This study investigated whether testicular artery Doppler-derived blood-flow parameters and circulating vascular endothelial growth factor (VEGF) concentrations are associated with semen quality and sperm freezability in clinically healthy dogs. Sixty-four privately owned male dogs underwent reproductive screening, semen collection, testicular Doppler ultrasonography, blood sampling, fresh and post-thaw semen analysis, and plasma VEGF quantification. Testicular artery Doppler parameters were not significantly associated with fresh or post-thaw semen quality or with most freezability outcomes. Plasma VEGF concentration was positively correlated with fresh linearity (LIN) (p = 0.034), straightness (STR) (p = 0.031), and beat-cross frequency (BCF) (p = 0.043). Higher VEGF concentrations were associated with greater post-thaw declines in progressive motility (PM) (p = 0.036), straight-line velocity (VSL) (p = 0.032), LIN (p = 0.001), STR (p = 0.005), and wobble (WOB) (p = 0.010). In multivariable analysis, VEGF was associated with linearity decline (B = 0.595, 95% CI: 0.254–0.937; p = 0.001). Circulating VEGF may therefore be associated with individual variation in canine sperm cryotolerance, whereas testicular artery Doppler assessment showed limited value.