In Vitro Supplementation of Glycine Improves Quality of Cryopreserved Bull Semen

Process of cryopreservation induces cell damages due to thermal and osmotic shocks. Addition of amino acids as cryoprotective agents in extender can reduce these damages. Therefore, present study was designed to evaluate the effect of glycine supplementation in extender on freezability of cryopreserved bull semen. For this purpose, three adult Sahiwal bulls were selected for semen collection by artificial vagina having 42 C (three weeks) (replicates; n=18). Collected semen was quickly shifted to laboratory for initial evaluation. Qualified semen ejaculates (>60% motility, >1mL volume, >0.5billion/mL conc.) were diluted in tris extender having 0 (control), 5, 10, 15 and 20mM of glycine. Semen was cooled to 4 C in 2 hours and kept for 4 hours for equilibration. Semen was filled in French straws at 4 C and kept in liquid nitrogen container. Highest percentages of post thaw sperm progressive motility and acrosome integrity were observed in extender containing 5mM of glycine compared to other treatments and control (P<0.05). However, sperm viability, chromatin integrity and plasma membrane integrity remained same. In conclusion, glycine addition at 5mM in extender improves quality of cryopreserved bull semen. Keywords: Glycine, amino acid, cryopreservation, bull semen.