Exploring the role of E.coli derived enzyme, Oxyrase, as an oxygen scavenger to improve the cryotolerance of spermatozoa of Sahiwal bull.

The current study intended to optimize the concentration of Oxyrase in the semen dilutor and to evaluate its effect on freezability of spermatozoa of Sahiwal bulls. Supplementation of Oxyrase at 0.125 IU/mL concentration significantly reduced dissolved oxygen (DO) in the dilutor to 4 ppm in 16–18 min at 35 °C. For supplementation studies, a total of 24 ejaculates were categorized into poor and good ejaculates categories (n = 12 each) based on their initial progressive motility. Each ejaculate was further divided into two aliquotes. The first aliquote was diluted with tris-egg yolk extender without Oxyrase (control group) whereas, in the treatment group, Oxyrase was supplemented at the concentration of 0.125 IU/mL of extender. The parameters evaluated include cholesterol and plasma membrane phospholipids (PMP) at fresh, while IPM, acrosomal and plasma membrane integrity, cholesterol, PMP and oxidative stress parameters like lipid peroxidation (LPO), total antioxidant capacity (TAC) and reactive oxygen species (ROS) were evaluated at pre-freeze and post-thaw stages. The IPM and acrosomal intactness were higher (p < 0.05) in treatment group at post-thaw stage in good ejaculates. Oxyrase supplementation resulted in lower (p < 0.05) cholesterol leakage in both categories and lower (p < 0.05) LPO in good ejaculates at post-thaw stage. No statistical difference in ROS was observed between control and treatment groups at all stages whereas, level of TAC was higher (p < 0.05) in the treatment group compared to control group at post-thaw stage of both categories. Therefore, Oxyrase as an oxygen scavenging agent could preserve the post-thaw quality of Sahiwal bull spermatozoa. [ABSTRACT FROM AUTHOR]