Abstract: The effects of resveratrol on the quality of frozen-thawed sheep semen were studied in this study.Semen was collected from six Yunnan semi-fine wool sheep using artificial vagina.The semen was diluted with the Optidyl extender supplemented with resveratrol with a concentration of 0,0.1,1,10,or 20 μmol/L,followed by loading into plastic straws and equilibration at a low temperature.Then,the straws were pre-frozen in liquid nitrogen vapor,followed by storage in liquid nitrogen for 30 days.After thawing for 30 seconds in a 37 ℃ water bath,the parameters including sperm motility,acrosome integrity,membrane integrity,distribution of phosphatidylserine (PS) and ROS were measured.The results showed that the post-thaw sperm total motility,progressive motility and the rate of sperm with curved tail were 76.14%±0.97%,43.56%±0.91% and 43.24%±1.68% in the 10 μmol/L resveratrol group,respectively,which were significantly higher than those in the other groups (P<0.05).However,when the concentration of resveratrol in the freezing extender was 20 μmol/L,the post-thaw total motility,progressive motility and the rate of sperm with curved tail were 21.78%±0.79%,25.23%±1.34% and 4.84%±0.68%,respectively,which were significantly lower than those in the other groups (P<0.05).The acrosome integrity of sperm frozen in the 10 μmol/L resveratrol group was best,which was 50.47%±0.91% and significantly higher than the other treatments (P<0.05).The results of PS distribution showed that the percentage of viable sperm in the 10 μmol/L resveratrol group was 46.43%±2.95%,and significantly higher than that in the 20 μmol/L group (31.14%±3.56%,P<0.05),but there was no significant difference with the other groups (P>0.05).In addition,the PS labeling rate of sperm in the 20 μmol/L resveratrol group (39.82%±3.38%) was significantly higher than those of the other groups (P<0.05).In terms of ROS production,this study demonstrated that the rate of viable sperm (ROS and PI were negative) in the 10 μmol/L resveratrol group (63.57%±0.71%) was significantly higher than that of the other groups (P<0.05),while the rate of viable sperm (32.45%±1.42%) in the 20 μmol/L resveratrol group was significantly lower than those of the other groups (P<0.05).In conclusion,the post-thaw quality of sheep semen could be improved after the addition of resveratrol to the freezing extenders,which might be related to the antioxidant properties of resveratrol.But,the cryoprotective effects of resveratrol dependents on its used doses,and the optimal concentration was 10 μmol/L based on this present study.However,excessively high concentration of resveratrol could aggravate cryodamage on sperm.In addition,the protective effects of resveratrol on sheep sperm still needs to be verified by in vitro fertilization and artificial insemination.

Key words: resveratrol; sheep semen; cryopreservation; antioxidant; reactive oxygen species