l‐Cysteine improves antioxidant enzyme activity,post‐thaw quality and fertility of Nili‐Ravi buffalo (Bubalus bubalis) bull spermatozoa

The effects of l ‐cysteine in extender on antioxidant enzymes profile during cryopreservation, post‐thaw quality parameters and in vivo fertility of Nili‐Ravi buffalo bull spermatozoa were studied. Semen samples from 4 buffalo bulls were diluted in Tris–citric acid‐based extender having different concentrations of l ‐cysteine (0.0, 0.5, 1.0, 2.0 and 3.0 mm ) and frozen in 0.5‐ml French straws. The antioxidative enzymes catalase, super oxide dismutase and total glutathione (peroxidase and reductase)] were significantly higher (P < 0.05) at pre‐freezing and post‐thawing in extender containing 2.0 mm l ‐cysteine as compared to other groups. Post‐thaw total motility (%), progressive motility (%), rapid velocity (%), average path velocity (μm s^?1), straight line velocity (μm s^?1), curvilinear velocity (μm s^?1), beat cross frequency (Hz), viable spermatozoa with intact plasmalemma (%), acrosome and DNA integrity (%) were higher with the addition of 2.0 mm l ‐cysteine as compared to other groups (P < 0.05). The fertility rates (59 versus 43%) were higher (P < 0.05) in buffaloes inseminated with doses containing 2.0 mm of l ‐cysteine than in the control. In conclusion, the addition of 2.0 mm l ‐cysteine in extender improved the antioxidant enzymes profile, post‐thaw quality and in vivo fertility of Nili‐Ravi buffalo bull spermatozoa.