Effects of Various Antioxidants on Cryopreserved Bull Sperm Quality

The objective of this study was to assess the effects of antioxidant supplement (A), fetuin (F), aminoacid (AS) and cysteine (CY) on the sperm parameters, plasma membrane integrity, chromatin damage and antioxidant activities after freeze-thawing. Ejaculates were split into five aliquots and extended to a final concentration of 15x10(6) spermatozoa/ml with the Tris base extender containing 0.5 ml A, 2 mg/ml F, 13% AS, 5 mM CY and no additive (C). The extended samples were equlibrated slowly to 4 degrees C during 4 h and then frozen using a digital freezing machine.. Frozen straws were thawed individually in water bath at 37 degrees C for 30 s to analyse progressive motility and sperm motion characteristics as well as membrane integrity. Biochemical assays were performed in a spectrophotometer using commercial kits. Chromatin damage was evaluated by Comet Assay. A, F, AS and CY did not show better result on the percentages of post-thaw sperm motilities. CY exhibited the greatest value of plasma membrane integrity (P<0.05). Total abnormalities were greater in C and F (17.5 +/- 0.57%; 15.5 +/- 1.98%, respectively; P<0.05). F had greater chromatin damage results (P<0.05). GPx activity was affected by type of antioxidant, notably CY yielded the lowest results when compared to the other groups (P<0.05). In conclusion, although using antioxidants does not have any influence on the sperm motility after thawing, A, AS and CY cause reduction at abnormal spermatozoa; CY exhibits the greatest cryoprotective activity on plasma membrane integrity and F caused an increase at chromatin damage.