Positive effects of trehalose and cysteine on ram sperm parameters

The aim of this study was to determine the effects of trehalose and cysteine on sperm motility, viability, mitochondrial activity and acrosome integrity during liquid storage of Merino ram semen. Ejaculates were collected using artificial vaginas from five Merino rams, microscopically evaluated and pooled at 37 °C. The pooled semen samples were diluted in a Tris-based extender, including cysteine (2 mM and 4 mM), trehalose (10 mM and 25 mM) and no antioxidant (control). Diluted semen samples were kept in tubes and cooled from 37 to 5 °C in a cold cabinet, and maintained at 5 °C. Cooled samples were evaluated for sperm motility, viability, mitochondrial activity and acrosome integrity at 0, 24, 48, 72 and 96 h. Extender supplemented with trehalose (10 and 25 mM) and cysteine (2 and 4 mM) led to higher motility in comparison to the control at 24, 48, 72 and 96 h of liquid storage (P < 0.05). Trehalose at the doses of 10 mM, 25 mM and 2 mM cysteine led to higher viability between 24-48-72 h and at 96 h of liquid storage (P < 0.05). Further, 4 mM of cysteine improved sperm viability rates at 24 and 48 h of storage compared to the control group (P < 0.05), and resulted in improved acrosome integrity rates compared to the control group at 72 and 96 h of storage (P < 0.05). Extender supplemented with 10 and 25 mM trehalose at 24 and 72 h and 4 mM cysteine at 24 and 96 h of storage led to higher sperm mitochondrial activity rates when compared to the control group (P < 0.05). In conclusion, the findings of this study show that trehalose and cysteine provided significant protection to ram sperm parameters during liquid storage.