Quercetin Supplementation during Boar Semen Thawing and Incubation Improves Sperm Characteristics

Elevated levels of reactive oxygen species (ROS) in the in vitro environment cause oxidative stress which leads to membrane damage, decreased fertility, and morphological deformities of spermatozoa. Antioxidants are often supplemented to reduce the impacts of oxidative stress on spermatozoa. Quercetin is a flavonoid that has a polyphenol structure able to donate electrons to stabilize free radicals, which can cause oxidative stress. The objective of this study was to evaluate the effects of supplementing quercetin (0.25, 0.50, 0.75 mM) during the thawing and incubation of frozen-thawed boar semen. Spermatozoa were evaluated for forward progressive motility (FPM), viability, and membrane lipid peroxidation (hydroperoxide) levels at 0, 2, 4, 6, 8, and 10 h after thawing. Spermatozoa supplemented with 0.25 mM quercetin had significantly higher (P < 0.05) motility (51.67 ± 8.50%) compared to all other treatment groups (32.22 ± 6.29%) at 10 h after thawing. Similarly, spermatozoa supplemented with 0.25 mM quercetin had significantly higher (P < 0.05) percent of viable cells (61.21 ± 2.44%) compared to all other treatment groups at 10 h after thawing. Hydroperoxide levels in 0.25 mM quercetin supplemented sperm had significantly (P < 0.05) lower levels (3.38 ± 0.88 μM/10⁷cells) compared to all other treatment groups. These results indicate that supplementing frozen-thawed boar semen with quercetin improves the sperm characteristics of forward progressive motility, viability and lipid peroxidation up to 10 h after thawing.