Effect of L-Cysteine in Tris-citric Egg Yolk Extender on Post-Thaw Quality of Nili-Ravi Buffalo (Bubalus bubalis) Bull Spermatozoa

Abstract

Present study was designed to investigate the effect of cysteine (0.0, 0.5, 1.0, 2.0 and 3.0 mM) in extender on the post-thaw quality of buffalo (Bubalus bubalis) bull spermatozoa. Semen was collected from five adult Nili-Ravi buffalo bulls of similar age group with artificial vagina (at 42°C) for three weeks (replicates). Qualifying semen ejaculates were split into five aliquots and diluted in tris-citric egg yolk extender containing either 0.0 (control) or 0.5 or 1.0 or 2.0 or 3.0mM cysteine at 37°C having 50 × 10 6 spermatozoa ml -1 . Diluted semen was cooled to 4°C in 2 hours and equilibrated for 4 hours at the same temperature. Cooled semen was filled in 0.5 ml French straws at 4°C, kept over liquid nitrogen vapours (5cm) for 10 min and then plunged in the liquid nitrogen for storage. Thawing of frozen semen was performed after 24 hours of cryopreservation at 37°C for 30 seconds. Sperm motility, viability, plasma membrane integrity and normal apical ridge were assessed at 0, 2 and 4 hour post thaw. Sperm motility, viability, plasma membrane and acrosomal integrity were highest (P<0.05) in extender containing cysteine 1.0mM at 0, 2 and 4 hour post thaw as compared to 0.5, 2.0, 3.0mM and control. In conclusion, L-cysteine (1.0mM) in extender improved the freezability of Nili-Ravi buffalo bull spermatozoa.