Impact of glutathione supplementation to egg yolk citrate extender on viability, plasma membrane integrity and fertility of cryopreserved bull semen

The present investigation aimed to study the effect of glutathione on the viability and membrane integrity of bull spermatozoa during the different stages of semen preservation. Sperm viability and the hypo-osmotic swelling test (HOST) were carried out after dilution, pre-freeze and post-thaw using an egg yolk citrate extender. Finally, the conception rate was determined after the insemination of fertile females with the thawed semen straws. The semen samples employed in this study were procured from four ostensibly healthy, crossbred, and fertile bulls. Two extenders were prepared: egg yolk citrate only (EYC, control) and egg yolk citrate plus glutathione (EYCG, glutathione concentration 0.5 mM). The semen underwent a subjective evaluation that included parameters such as viability, the status of plasma membrane integrity (PMI) and transmission electron microscopy following the initial extension, equilibration with glycerol, and subsequent thawing. The results revealed that, following initial extension, pre-freeze and post-thawing, the viability and PMI percentages were significantly (p<0.05) elevated in the EYCG group compared to the EYC group. The EYCG group exhibited a greater percentage of normal spermatozoa with intact and moderately swollen plasma membranes, compared to the control group. The results showed that cows inseminated with EYCG attained a significantly (p<0.05) higher conception rate than those inseminated with EYC semen. It was concluded that the addition of Glutathione (0.5 mM) into the Egg Yolk Citrate extender conferred a protective effect against cryodamage during cryopreservation and enhanced the quality parameters of post-thaw bull spermatozoa, thereby improving the cryopreservation outcomes of spermatozoa, which, in turn, would augment the conception rate under field conditions.