The addition of crocin in the freezing medium extender improves post-thaw semen quality

Semen cryopreservation is arguably the most important method or technique contributing to the advancement of modern animal production. However, the quality of sperm after thawing is still highly variable. The addition of antioxidant compounds to the freezing medium has been used customarily to counteract the harmful effects of Reactive Oxygen Species (ROS) that are produced during the freeze/thaw process. Crocin, a potent antioxidant, improves the fertilizing capacity of spermatozoa. In this study, we evaluated the potential of crocin (0, 0.5 and 1 mM) as an extender additive to diminish the damaging effects of cryopreservation on bovine spermatozoa. Post-thaw semen quality was assessed by means of motility, viability and lipid peroxidation (LPO). We further investigated the effect of crocin supplementation upon freezing on sperm quality parameters during their incubation at 37°C for up to 2 hr. Overall, the data assessment indicates that crocin facilitated a general improvement of the quality of freeze/thawed spermatozoa, under the present experimental conditions. Crocin (1 mM) maintained a higher percentage of alive spermatozoa with intact acrosome with rapid and progressive motility, compared to the control extender. Moreover, the spermatozoa cryopreserved in the presence of crocin exhibited higher values in CASA kinematic parameters (VCL, VSL, VAP, ALH) immediately after thawing. Furthermore, the positive effect of crocin on motility parameters was also sustained over a period of 2 hr incubation at 37°C. This effect of crocin may be attributed to the observed inhibition of LPO during the incubation period. Thus, the results indicate that the addition of crocin (especially at a final concentration of 1 mM) in the freezing extender medium may benefit the preservation of the quality parameters of spermatozoa that are compromised by the freeze/thaw heat shock and the stress during handling for IVF or artificial insemination.