Effect of cysteine addition to the freezing extender on the progressive motility, viability, plasma membrane and DNA integrity of Nili-Ravi buffalo (Bubalus bubalis) bull spermatozoa

Abstract

The effect of cysteine addition to the freezing extender on the progressive motility, viability, plasma membrane and DNA integrity of buffalo bull spermatozoa was studied. Semen from three Nili-Ravi buffalo bulls of similar age group was collected with artificial vagina. Qualifying ejaculates were split in three aliquots for dilution (50 × 106 spermatozoa ml–1) with tris-citric acid extender containing either 0.0, 0.5, 1.0 mM cysteine. Extended semen samples were cooled and equilibrated before cryopreservation. Progressive motility, plasma membrane integrity, viability and DNA integrity were assessed at 0, 2 and 4 hours post-thaw incubation (37°C). Sperm progressive motility and plasma membrane integrity of buffalo bull spermatozoa were higher (P < 0.05) in extender containing 1.0 mM cysteine than those with 0.5 mM or 0.0 mM at 0, 2 and 4 hours post-thaw. Sperm viability and DNA integrity were higher (P < 0.05) in extender containing 0.5 mM and 1.0 mM cysteine than those with 0.0 mM cysteine at 0, 2 and 4 hours post-thaw. The in vivo fertility rates were similar (P > 0.5) with semen cryopreserved in extender containing cysteine (1.0 mM) compared to control. It is concluded that addition of 1.0 mM cysteine to the tris-citric acid extender improved the post-thaw in vitro quality of buffalo bull spermatozoa.