Effect of Mifepristone, Sericin and Taurine in Tris Extender on Oxidative Markers and Quality of Fresh and Frozen-Thawed Bovine Spermatozoa

Abstract

This study was carried out on semen of 3 Gir and 3 Murrah bulls. Semen ejaculates with >75 % initial motility (n=7 per bull; 21/breed; total 42) were split-diluted at 100 million sperm per ml using Tris-citric acid-fructose-egg yolk-glycerol (TFYG) extender without and with Mifepristone (10 µg/ml), Sericin (5 mg/ml) and Taurine (4 mg/ml) as additives. French mini straws were filled and sealed using IS4 system, and frozen in liquid nitrogen vapour using a programmable biofreezer after 4 hrs of equilibration. The straws were thawed in water bath at 37°C for 30 sec. The overall mean per cent sperm motility observed in freshly diluted and frozen-thawed semen, irrespective of antioxidants, were 83.57±0.51 and 46.73±0.67 in Gir, and 83.15±0.54 and 48.81±0.82 in Murrah bulls, respectively. The corresponding per cent capacitated sperm (B+AR pattern) in chlortetracycline (CTC) fluorescence assay were 17.77±0.53 and 34.44±0.95 in Gir, and 18.00±0.51 and 31.20±0.82 in Murrah bulls. The mean seminal plasma MDA (µmol/ml) activity on dilution and at post-thaw stage were 18.83±0.25 and 20.59±0.28 for Gir, and 19.32±0.26 and 21.76±0.31 for Murrah bulls, respectively. The corresponding means for SOD (U/ml) were 2.94±0.05 and 2.45±0.03 for Gir, and 2.35±0.06 and 1.97±0.05 for Murrah bulls, and the GPx (nmol/min/ml) 493.85±8.31 and 438.87 ±8.13 for Gir, and 508.82±8.71 and 452.83±8.20 for Murrah bulls, respectively. All the parameters differed significantly between stages and between extender-additives. MDA activity and capacitated sperm were significantly (p<0.05) lower, while SOD and GPx were higher with improved sperm motility (p<0.01), particularly at post-thaw stage, in extender fortified with Mifepristone than the control, but statistically similar to extender fortified with Sericin and Taurine. In conclusion, Mifepristone 10 µg/ml in TFYG extender appeared to be the best in terms of antioxidant and capacitation inhibitor followed by Taurine 4 mg/ml and Sericin 5 mg/ml over control extender against ROS mediated injuries during cryopreservation of both cattle and buffalo semen as assessed by sperm motility, CTC assay and oxidative makers.