Fortification of Tris Extender with Mifepristone, Sericin and Taurine Improves Velocity and Kinematics of Fresh and Frozen-thawed Bovine Spermatozoa

Abstract

Background: The evaluation of bull fertility essentially involves semen analysis and conception rates among inseminated females. The conventional evaluation is relatively imprecise, time consuming and subjected to individual variations, while computer assisted sperm analysis (CASA) is a quite faster, precise and objective tool to identify differences in sperm motility and velocity/kinematics attributes and avoids subjective errors. The present study was planned to evaluate and compare the CASA traits of fresh and frozen-thawed semen of Gir and Murrah bulls in Tris extender without and with different antioxidant additives by adopting Biovis CASA.Methods: The semen ejaculates with greater than 75% initial motility from 3 Gir and 3 Murrah bulls were split-diluted at 100 million sperm per ml using Tris-citrate-fructose-yolk-glycerol (TFYG) extender without (control) and with three antioxidant additives, viz., Mifepriston (10 µg/ml), Sericin (5 mg/ml) and Taurine (4 mg/ml), were filled in French mini straws and frozen in liquid nitrogen vapour using a programmable biofreezer. The freshly diluted and frozen-thawed semen samples were assessed for sperm motion characteristics, velocity/kinematics using Biovis CASA. Result: The mean percentages of total motile spermatozoa, irrespective of additives, in freshly diluted and frozen-thawed semen were 85.50±0.92 and 48.76±1.69 for Gir bulls and 85.03±0.72 and 52.61±1.46 for Murrah bulls, respectively. The mean total motile as well as rapid and slow progressive motile sperm percentage were significantly enhanced by fortification of TFYG extender with Mifepristone than in control extender, while values for Sericin and Taurine were intermediary and statistically similar to Mifepristone. The per cent decline in total motile sperm due to freezing-thawing was more or less same in both the breeds for all the extender additives, being lowest in Mifepristone supplemented extender in cattle (32.27 vs 48.81%) and buffalo (31.27 vs 43.14%) semen. The rapid and slow progressive motile sperm also followed the same pattern. The values of VAP and VCL were significantly (p less than 0.05) higher and VSL lower in Murrah than Gir breed at post-thaw stage. The overall mean linearity (%), straightness (%), beat-cross frequency (hz), lateral head displacement (µm), wobbling index (%), dancing velocity (µm2/s) and dancing mean (µm2/s) of sperm were higher in Murrahs than in Gir semen with significant (p less than 0.01) difference at post-thaw stage. The fortification of extender with Mifepristone improved all these traits at post-thaw stage compared to other additives and control TFYG extender. The per cent decline in these traits due to freezing stress was much lower in buffalo sperm than the cattle sperm particularly with Mifepristone fortification. It was concluded that freezing-thawing stress adversely affected the motion and kinematics of both cattle and buffalo sperm and that Tris extender fortified with antioxidant additives, particularly Mifepristone @ 10 µg/ml, protected sperm from adverse effect of dilution and cryopreservation with improved post-thaw sperm quality.