This investigation was carried out to study the correlation of sperm quality parameters with antioxidant and oxidant status of buffalo bull semen during various stages of cryopreservation. Semen samples were evaluated for sperm parameters (mass motility [MM], concentration [CON], progressive motility [PM], viability [VIB], acrosomal integrity [AI] and hypo-osmotic swelling [HOS] response), antioxidants (superoxide dismutase [SOD], catalase [CAT], glutathione peroxidase [GPx] and total antioxidant capacity [TAC]) and oxidants (Lipid peroxidation [LPO] and reactive oxygen species [ROS]) at fresh, pre-freeze and post-thaw stages. Sperm parameters (PM, VIB, AI and HOS response) and antioxidants (SOD, CAT and TAC) were significantly (p < .05) reduced at fresh stage, and oxidants (LPO and ROS) were significantly (p < .05) increased at pre-freeze and post-thaw stages. At fresh stage, MM was negatively correlated with LPO (p < .05), and CON was positively correlated with SOD, TAC and CAT, negatively correlated with LPO and CAT was positively (p < .01) correlated with VIB and HOS response. At pre-freeze stage, CAT was positively correlated with PM and AI (p < .05), and AI was negatively (p < .05) correlated with ROS. At post-thaw stage, CAT was positively correlated with PM, VIB, HOS response and AI,, and LPO was negatively correlated with HOS, AI and VIB. The study of correlations of these parameters at different preservation stages with bull fertility may play an important role in developing models for predicting future fertility of bulls in the absence of conception rate data.

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The present investigation was carried out to study the effect of various levels of dissolved oxygen (DO) on reactive oxygen species (ROS) and cryocapacitation-like changes in bull sperm. Egg yolk-Tris-glycerol (EYTG) extender was split into four subextenders; viz., Extender I (control; no flushing with liquid nitrogen (LN )), Extender II, Extender III and Extender IV were flushed with LN for 40, 16 and 8 min, respectively. The DO levels were standardized to 11.7, 2, 4 and 8 ppm, respectively, in control (Extender I), Extender II, Extender III and Extender IV. Ejaculates with mass motility of ≥ 3+ were divided into group I (diluted with Extender I), group II (diluted with Extender II), group III (diluted with Extender III) and group IV (diluted with Extender IV) up to 80 × 10 sperm/ml. Extended semen samples were packed in French mini straws (0.25 ml), equilibrated and cryopreserved. Semen samples were evaluated at prefreeze and post-thaw stage for various parameters (DO, progressive motility (PM), viability (VIB), acrosomal integrity (AI), hypo-osmotic swelling (HOS) test, ROS, cholesterol (C) and phospholipid (P). The percentage of PM, VIB, AI, HOS test, cholesterol (C) and phospholipid (P) levels, and capacitated sperm were significantly (p < 0.05) higher in groups III and IV as compared to groups I and II. However, the acrosome-reacted sperm (%; pattern AR) were significantly (p < 0.05) decreased in group III as compared to all other groups. Besides the proportion of sperm displaying tyrosine-phosphorylated pattern, EA (fluorescence at both equatorial and anterior acrosomal regions, i.e. high capacitation level) was significantly (p < 0.05) reduced in group III compared to all other groups. In conclusion, varying DO levels in the extender significantly affect sperm quality, ROS production and capacitation-like changes in bulls.

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