LAUSR

The present study was undertaken to determine the efficacy of partial deoxygenation of extender at constant temperature (35°C) in freezability of crossbred bull semen. The dissolved oxygen (DO) levels were reduced by the use of newly developed technique of nitrogen effervescence at a flow rate of 2–3 bubbles per second. Four different levels of oxygen in semen extender, that is 11.7, 2, 4 and 8 ppm as control (Group‐I), Group‐II, Group‐III and Group‐IV, respectively, were used to assess the effect of partial deoxygenation on semen quality parameters. The 4 ppm level of DO resulted in higher (p < 0.05) progressive motility in comparison with non‐treated group at post‐thaw stage, whereas reduction up to 2 ppm resulted in drastic fall in motility. Oxidative stress status revealed low superoxide dismutase (SOD) and total antioxidant capacity (TAC) in Group‐II, whereas higher (p < 0.05) SOD and TAC activities were observed in Group‐III in comparison with non‐treated group at pre‐freeze and post‐thaw stages. The sperm‐zona binding at 4 ppm level of DO was significantly higher than control group, 2 and 8 ppm levels of DO. In conclusion, reduction of DO in the extender up to 4 ppm reduced oxidative stress and improved in vitro fertility of crossbred bull spermatozoa.