Enzymatic Antioxidants and Their Differential Response to Cryopreservation in Japanese Quail Semen

A triad of enzymatic antioxidants viz., catalase (CAT), superoxide dismutase (SOD) and glutathione peroxidase (GPx) constitutes a first line of defence against any redox imbalances in the semen. Cryopreservation enabling long term storage of semen also prompts generation of surplus reactive oxygen species (ROS) in the cells with waned antioxidants, hampering the full exploitation of this process. With Japanese quail having all the potential to satisfy the steeply growing poultry demand, there is a need for its propagation via sperm preservation and assisted reproduction. Therefore, current study aimed at investigating enzymatic antioxidants in the Japanese quail semen, level of decline in their activity during cryopreservation and any intra-species variation in their levels. Moreover, malonaldehyde (MDA) levels in fresh and cryopreserved semen of individual birds were taken into account. Semen was collected separately from seven mature males, diluted with NaCl extender (1:15) and cryopreserved. Analysis of sperm and seminal plasma was done at fresh collection, post-dilution, post-cooling, post-equilibration and post-thaw stages of freezing. The results confirmed the presence of CAT, SOD and GPx in fresh sperm and seminal plasma, their decline (p < 0.05) at all stages of cryopreservation and intra-species variation (p < 0.05) with respect to freeze-tolerance. Furthermore, significant increase was recorded in MDA levels at varying rates among individual quails during semen cryopreservation. In conclusion, Japanese quail sperm and seminal plasma exhibit enzymatic antioxidant activities to monitor ROS generation and performance of these antioxidants is severely affected by freezing process with intra-species variation and rise (p < 0.05) of lipid peroxidation (LPO).