Cryopreservation is associated with the production of reactive oxygen species, which leads to lipid peroxidation of the sperm membrane and consequently a reduction in sperm motility and decreased fertility potential. The aim of this study was to determine the optimal concentration of L-cysteine needed for cryopreservation of boar semen. Twelve boars provided semen of proven motility and morphology for this study. The semen was divided into four portions in which the lactose-egg yolk (LEY) extender used to resuspend the centrifuged sperm pellet was supplemented with various concentrations of L-cysteine to reach 0 mmol L⁻¹ (group I, control), 5 mmol L⁻¹ (group II), 10 mmol L⁻¹ (group III) and 15 mmol L⁻¹ (group IV). Semen suspensions were loaded in straws (0.5 mL) and placed in a controlled-rate freezer. After cryopreservation, frozen semen samples were thawed and investigated for progressive motility, viability using SYBR-14/EthD-1 staining and acrosome integrity using FITC-PNA/EthD-1 staining. There was a significantly higher (P < 0.01) percentage of progressive motility, viability and acrosomal integrity in two L-cysteine-supplemented groups (group II and group III) compared with the control. There was a biphasic effect of L-cysteine, with the highest percentage of progressive motility, viability and acrosomal integrity in group III. In conclusion, 5 or 10 mmol L⁻¹ was the optimum concentration of L-cysteine to be added to the LEY extender for improving the quality of frozen–thawed boar semen.


Keywords:

antioxidant; boar semen; cryopreservation; L-cysteine

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