Impact of Astaxanthin Concentration in Extender on Sperm Kinetics and Lipid Peroxidation After Cryopreservation in Beef Bulls

Cellular damage caused by changes in temperature and osmolarity during cryopreservation primarily results in excessive generation of reactive oxygen species (ROS). These damages compromise the plasma membrane and reduce sperm fertility. Antioxidants help mitigate these effects. Astaxanthin stands out for its high capacity to protect cellular integrity. The aim of this study was to evaluate the effects of adding astaxanthin (ASTX) to commercial extender on the quality of bovine semen after cryopreservation. Four ejaculates were collected from 12 Nellore bulls, totalling 48 samples. Sperm kinetics, concentration and morphology of the samples were evaluated. The semen sample was then divided into three aliquots and diluted in commercial extender: control (without astaxanthin) and addition of 1 μmol (ASTX1) or 2 μmol (ASTX2) of ASTX. After cryopreservation, the samples were re-evaluated immediately after thawing and after 30 min of incubation at 46°C (rapid thermal resistance test) regarding sperm kinetics, plasma and acrosomal membrane integrity, mitochondrial membrane potential and oxidative stress levels (TBARS). Rapid sperm percentage and amplitude of lateral head displacement were higher (p < 0.05) in the ASTX groups than in the control group. Total motility was higher in the ASTX1 group than in the control group. Although there was no difference in plasma membrane integrity, acrosomal membrane integrity or mitochondrial membrane potential between treatments, lipid peroxidation was lower (p = 0.041) in the ASTX1 and control groups than in the ASTX2 group. We conclude that the inclusion of ASTX at a concentration of 1 μmol in the extender improves sperm kinetics after thawing in beef bulls semen.