Effect of anti-oxidant supplementation on post-thaw sperm characteristics, membrane integrity, migration capability and lipid peroxidation in bull semen

A study was conducted to assess the influence of natural (vitamin E) and synthetic (butylated hydroxyl toluene; BHT) anti-oxidants on post-thaw semen characteristics, migration ability and functional integrity and lipid peroxidation following freezing and thawing in crossbred HF bulls. Semen was collected from 3 crossbred bulls (HFxT) twice a week and 18 collections (6 collections per bull) were utilized in this study. After initial evaluation each semen sample was split into 3 equal fractions and diluted in tris egg yolk extender containing either vitamin E @0.3mg/ml (TEY-E), BHT @2.0mM/ml (TEY-B) or without any additive (TEY-C) which acted as control. Filling and sealing of individual diluted semen samples in PVA straws, equilibration at 4 degrees C for 4h, freezing in programmable freezer and plunging of straws into liquid nitrogen were followed as per standard procedure. Thawing of semen was performed at 37 degrees C for 30 sec. Post-thaw semen characteristics such as progressive motility, live sperm percent and acrosomal integrity were significantly higher and sperm abnormalities were significantly lower in samples containing vitamin E and BHT over the control. The sperm penetration distance (mm/20min) was highest in TEY-E (50.19 +/- 1.36) followed by TEY-B (40.94 +/- 1.54) and the least in TEY-C (36.83 +/- 1.49) diluents. Similarly the HOS positive spermatozoa (%) were significantly higher in vit E (49.21 +/- 0.97) and BHT (48.12 +/- 0.89) added extenders over the control (37.86 +/- 1.39).The MDA levels (mu mol/ml) increased significantly in non-antioxidant added samples (0.60 +/- 0.05) over vit E (0.11 +/- 0.01) and BHT (0.19 +/- 0.02) containing samples following thawing. The results revealed that supplementation of vit E and BHT to tris egg yolk extender improve the post-thaw semen quality in bulls.