Browsing by Author "Ngou, Athanas Alex"

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Effect of partial deoxygenation of semen dilutor with oxyrase on freezability of bull spermatozoa
(ICAR-Indian Veterinary Research Institute, 2019) Ngou, Athanas Alex
Poor survival of the spermatozoa after cryoprcscrvation is vastly contributed by damages resulted from temperature stress, osmotic stress and oxidative stress. The current study intended to optimize the concentration of Oxyrasc (partial deoxygenating agent) in the semen di tutor and to evaluate its el feet on frcczability of Sahiwal bull spermatozoa. The selected ejaculates (n=24) were categorized into poor ejaculates (n= I 2) and good ejaculates (n= 12) based on their initial progressive motility. Besides that, each selected ejaculate was divided into two groups and diluted with tris-egg yolk extender containing no Oxyrasc or 0.125 lU/mL of Oxyrasc for the control and treatment groups, respectively. Parameters evaluated were bacterial load, seminal plasma cholesterol (SPC) and plasma membrane phospholipids (PMP) at fresh stage while individual progressive motility (IPM). acrosomal integrity and plasma membrane integrity (PM I) at post-dilution stage. At pre-freeze stage dissolved oxygen (DO). IPM. acrosomal integrity, PM1. SPC, PMP and oxidative stress (LPO. TAC and ROS) were evaluated. Bacterial load and all the pre freeze parameters were again evaluated at post-thaw stage. Oxyrase al 0.125 ILI/mL concentration significantly reduced DO in the dilutor to 4 ppm in 16-18 minutes at 35"C. Significantly higher progressive motility was observed in the Oxyrasc treated groups at post-thaw stage of good ejaculates category in comparison to control. The lowest decline in progressive motility from post-dilution to post-thaw was observed in the Oxyrasc treated group of good ejaculates category and the highest decline was in the control group of poor ejaculates category. The per cent intact acrosome differed significantly between treatment and control groups of good ejaculates category at post-thaw stage. Significant (p<0.05) difference in plasma membrane integrity was observed at pre-freeze stage of poor ejaculates category between the treatment group and control group. The lowest decline in plasma membrane intactness from post-dilution to post-thaw was observed in treatment group of good ejaculates category while the highest decline was in control group of poor ejaculates category. The trend of increase in cholesterol efflux was significantly observed from fresh to pre-freeze stage and post-thaw stage. However, the treatment groups at post-thaw stage in both categories had significantly less cholesterol efflux in comparison to their control groups. No significant difference in plasma membrane phospholipids concentration was observed between the Oxyrasc treated and non-treated groups at all stages oi both ejaculate categories. The treatment groups of good ejaculate category had significantly (p<0.05) lower levels of lipid peroxidation in comparison to their control group at pre-freeze and post-thaw stages. The level of antioxidant capacity was significantly (p<0.05) higher in the treatment groups compared to control groups at post-thaw stage of both categories. Moreover, the lowest decline in antioxidant capacity from pre-freeze to post-thaw was estimated in the treatment group of good category and the highest decline found in the control group of poor ejaculate category. No statistical diflcrence in ROS production was observed between the control and the treatment groups at all stages of both ejaculate categories. The level of bacterial contamination was significantly lower in treatment group than in control at post thaw in good ejaculates category. Consequently, addition of Oxyrasc in dilutor significantly increases frcczability of Sahiwal bull spermatozoa by improving post-thaw motility, acrosome integrity, TAC and reducing cholesterol efflux, LPO and bacterial load in good ejaculates, furthermore, addition of Oxyrasc in poor ejaculates reduces cholesterol efflux and increase TAC but do not improve the frcczability to a significant level. Therefore, reduced dissolved oxygen in dilutor before cryopreservation improves post thaw semen quality parameters and may have the potential to overcome freeze-thaw damages due to excess reactive oxygen species.