The aim of the present study was to evaluate the effects of quercetin as an antioxidant supplement on frozen-thawed ram epididymal sperm quality. Quercetin is a type of flavonoid antioxidant that is found in plants, with the ability to scavenge free radicals. Twenty testicles from mature rams were collected from a nearby slaughterhouse immediately after slaughter. Epididymal spermatozoa were recovered from the caudal of epididymides by injecting Bracket and Oliphant’s (BO) medium retrogradely through the ductus deferens and extended with a tris egg-yolk-based extender and supplemented with 0, 5, 10, 15, 20, and 50 µg/mL quercetin. Following equilibration, the straws were frozen, and then plunged into liquid nitrogen. After thawing, optimized concentrations of quercetin were deﬁned based on their viabilities and used to assess fertilization and developmental potential. The results showed that the viability of frozen-thawed spermatozoa significantly increased by using 5 and 10 µg/mL quercetin in the freezing extender. However, total and progressive motility of frozen-thawed spermatozoa were not affected by 5 and 10 µg/mL quercetin in comparison with control (0 µg/mL). The mean number of zygote, morula, and blastocyst stage embryos increased significantly by using 5 and 10 µg/mL quercetin compared with other frozen-thawed treatments(P <0.05). However, the blastocyst rate of fresh sperm was significantly higher (P <0.05). In conclusion, to improve the quality of frozen-thawed ram epididymal spermatozoa, 5 and 10 µg/mL quercetin appears to be an attractive option. Further studies are suggested to understand the synergistic effect of quercetin with other antioxidants to improve the ram freezing–thawing process.
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