Effect of glycine-enriched freezing medium on post-thaw quality and fertility of Murrah buffalo (Bubalus bubalis) bull semen

This study was designed to evaluate the effect of glycine supplementation (0.0, 5.0, 10.0, 15.0, 20.0 and 25.0 mM) in freezing media on post-thaw quality of buffalo bull spermatozoa. Thirty-six semen ejaculates from six breeding Murrah buffalo bulls were collected using artificial vagina. Ejaculates having ≥ 70% sperm motility, ≤ 20% morphological abnormalities and > 500 million/ml concentration were diluted in Tris-egg yolk extender containing selected concentrations of glycine and control and cryopreserved following established protocol. The post-thaw semen was examined for CASA-based sperm motility and kinematics, viability, plasma membrane integrity, acrosome integrity, mitochondrial membrane potential and LPO. Statistical analysis was done using the IBM SPSS 20.0 software and Microsoft excel 2021. The total motility, progressive motility and plasma membrane integrity were higher (P < 0.05) in cryodiluent containing 20.0 mM of glycine in comparison to other concentrations and control. Regarding sperm kinematics, VAP was higher (P < 0.05) at 20.0 mM, VCL at 20.0 mM and 25.0 mM and VSL at 15.0 mM and 20.0 mM compared to other concentrations and control, respectively. Supplementation of glycine at 20.0 mM and 25.0 mM resulted in higher (P < 0.05) proportion of viable sperm. Mitochondrial membrane potential was higher (P < 0.05) at 15.0–25.0 mM glycine concentrations compared to remaining concentrations and control. MDA profiles were lower (P < 0.05) in all glycine supplemented groups, with lowest levels at 20.0 mM and 25.0 mM than in control. Sixty animals were inseminated using best evolved extender having glycine (20.0 mM) and control (n = 30 each). The conception rates were non-significantly (P > 0.05) higher using extender containing glycine than in control (53.3% vs 40%). In conclusion, addition of 20.0 mM glycine in freezing medium improved the sperm characteristics and conception rate of post-thaw Murrah buffalo bull semen.