Effects of zinc chloride on boar sperm quality during liquid storage at 17°C

OBJECTIVES: The aim of this study was to evaluate the effects of zinc chloride (ZnCl(2)) at 20, 50, 100, and 200 μg/mL on the quality of seminal plasma‐free boar sperm stored at 17°C for 7 days and to explore the underlying mechanisms. METHODS: Boar sperm were collected and incubated in non‐capacitation/capacitation medium to analyze sperm quality. RESULTS: In the non‐capacitated state, the addition of ZnCl(2) at 20 and 50 μg/mL improved the survival rate and plasma membrane integrity of boar sperm (p < 0.05). Compared to the control group, the addition of ZnCl(2) significantly increased total antioxidative capacity and CuZn superoxide dismutase activity, while reducing the malondialdehyde content (p < 0.05). ZnCl(2) at 100 and 200 μg/mL significantly decreased sperm motility, protein kinase A (PKA) substrate phosphorylation, and tyrosine phosphorylation. These proteins were mainly located on the mid‐pieces of the flagellum. The addition of ZnCl(2) at 20 and 50 μg/mL conveyed a protective effect to boar sperm stored at 17°C. Furthermore, ZnCl(2) at 100 and 200 μg/mL inhibited sperm motility via tyrosine phosphorylation, thus preventing the ‘capacitation‐like’ state. In the capacitated state, there was no change in PKA substrate phosphorylation and tyrosine phosphorylation of the mid‐pieces of the flagellum compared to the control groups, indicating that the addition of Zn(2+) did not negatively affect capacitation of preserved sperm. CONCLUSIONS: ZnCl(2) showed protective capacity to the preservation extender used for boar sperm during the process of 17°C storage, and the optimal concentration of ZnCl(2) for the preservation extender was 100 μg/mL.