Antioxidant effects of Thymus vulgaris extraction on viability and membrane integrity of freeze-thawed ram spermatozoa

The antioxidant effects of Thyme (Thymus vulgaris L.) extract in semen extenders against cryo-damage to ram sperm have not yet been studied. Therefore the aim of the current study was to determine the effects of different concentrations of Thyme extraction as a natural antioxidant on frozen- thawed ram sperm viability and plasma membrane integrity. Semen samples were collected twice a week from four rams. Samples were then pooled and diluted with Tris based extender supplemented with different concentrations of Thymus vulgaris (0, 2, 4, 8, 12 and 16ml in dL diluents solution). Following equilibration, the straws were frozen, and then plunged into the liquid nitrogen. After freezing-thawed, viability and plasma membrane integrity were evaluated. The results showed that plasma membrane integrity was higher (p < 0.05) in 4 and 8 mL/dL extract groups (54.21 ±3.15% and 56.11 ±4.07%, respectively) compared to control, 12 mL/dL and 16 mL/dL extract groups (43.41 ±2.63, 40.43 ±3.31% and 39.93 ±2.93%, respectively). Number of viable sperm was increased (P < 0.05) in the extender containing 4 mL/dL extract (55.13 ±3.35%) compared to control, 12 and 16 mL/dL extract groups (46.08 ±3.32%, 43.21 ±3.56% and 39.31 ±3.23%, respectively). In conclusion our data showed that supplementation of semen extender with 4 mL/dL Thymus vulgaris extract significantly improved the quality of frozen-thawed ram semen, probably due to polyphenolic compounds having antioxidant activity.

Keywords:

Antioxidant , Thymus vulgaris extract , membrane integrity , frozen- thawed ram sperm