Effect of cysteine supplementation in semen extender on freezability and fertility of Murrah buffalo semen

The present study was designed to evaluate the effect of different concentrations of cysteine on freezability and in vivo fertility of buffalo bull spermatozoa. Twenty-four ejaculates from four healthy breeding Murrah buffalo bulls were collected using artificial vagina. Qualified semen ejaculates (1-2 ml volume; >70% initial progressive motility; >4 mass activity; 1.0 billion/ml concentration) were diluted with Tris-citric acid extender containing 0.0 mM (control), 2.5 mM, 5.0 mM, 7.5 mM and 10.0 mM cysteine at 37oC and cryopreserved following standard protocol. The post-thaw semen was evaluated for CASA-based sperm motion traits, viability, plasma membrane integrity, acrosome integrity and oxidative stress. The sperm total and progressive motility, viability and plasma membrane integrity were higher in extender containing 2.5 mM/ml of cysteine compared to other concentrations. Acrosome integrity exhibited no difference in all groups with cysteine compared to control. Regarding sperm kinematics, addition of cysteine (2.5 mM/ml and 5.0 mM/ml) to extender significantly improved VCL and VAP as compared to other groups. The oxidative stress (MDA production) was significantly lower in extender supplemented with cysteine (5.0 mM/ml and 2.5 mM/ml) than in other groups. A total of 40 artificial inseminations were performed with the best evolved cysteine-supplemented extender (2.5 mM) based on the evaluation of post-thaw sperm attributes and control (20 each). In vivo fertility rates of buffalo semen were recorded non-significantly higher with extender supplemented with cysteine (2.5 mM; 55%) compared to control (0.0 mM; 45%). In conclusion, supplementing 2.5 mM cysteine in extender improved the post-thaw quality of Murrah buffalo bull semen.