Effects of cysteamine supplementation on cryopreserved buffalo bull semen quality parameters

This work aimed to determine the effect of cysteamine (25, 50, 100 and 200 μM) incorporated during dilution on frozen thawed buffalo semen quality. Semen was collected twice weekly for 7 consecutive weeks from three Egyptian buffalo bulls using an artificial vagina. Semen samples were pooled and extended with a Tris-based extender, cooled, equilibrated and finally frozen in liquid nitrogen. The diluted semen was evaluated for motility, viability, morphology, plasma membrane and DNA integrity, in addition to oxidative stress and in vitro fertilizing capability. The post thaw motility and velocity parameters noticeably increased with different concentrations of cysteamine (mainly 100 μM) during different incubation periods. The post thaw sperm viability and normality significantly (p < 0.05) improved with concentrations of 50 and 100 μM. Plasma membrane integrity substantially increased at all concentrations of cysteamine. Cysteamine reduced alanine aminotransferase (at all concentrations), aspartate aminotransferase (at 25-100 μM), and creatine kinase (at 100 and 200 μM). Cysteamine at a concentration of 100 μM noticeably enhanced the total antioxidant capacity and glutathione peroxidase and decreased nitric oxide production. Cysteamine, at concentrations of 100 and 200 μM, increased the DNA intensity in the comet head (%) and decreased the DNA % in the comet tail. The comet tail length and moment substantially decreased at concentrations of 50-200 μM. Cysteamine did not affect the in vitro fertilizing capability of sperm. In conclusion, cysteamine incorporation (mainly at a concentration of 100 μM) in buffalo semen extender showed varying protective effects on different sperm parameters against cryo-damage; however, it did not affect the in vitro fertilizing capacity of sperm.