The effect of supplementing freezing extender with Mn2+-, Zn2+- or Cu2+-nanosuccinate on select post-thaw characteristics of ram semen

Abstract

The effects of Mn²⁺-, Zn²⁺- or Cu²⁺-nanosuccinate added to freezing extender on select post-thaw semen characteristics were determined in six Texel rams (aged 2–4 years) during seasonal anestrus (April-May). Ejaculates (n = 6 per ram) collected into an artificial vagina were divided into ten isovolumetric fractions each. Semen was diluted in lactose-yolk-tris-citrate-glycerin medium and nanosuccinates (Mn²⁺- and Zn²⁺-nanosuccinate: 0.0 (control), 2.5, 5.0 and 7.5 μg/l; Cu²⁺-nanosuccinate: 0.0 (control), 1.25, 2.5 and 3.75 μg/l) were added to semen extender. Extended semen was loaded into 0.25-ml straws and frozen in liquid nitrogen. After thawing, sperm motility parameters were determined with computer assisted semen analysis (CASA), and the activity of superoxide dismutase (SOD), glutathione peroxidase (GPx) and catalase (CAT) was measured with a spectrophotometric technique. The addition of 5.0 μg/l of Mn²⁺- and Zn²⁺-nanosuccinate significantly increased the sperm progressive motility and both 2.5 and 5.0 μg/l improved sperm motion kinetics. Further, both nanosuccinates at a dose of 5.0 μg/l significantly decreased SOD activity and stimulated an increase in GPx and CAT activity in semen samples. Alternatively, the addition of Cu²⁺-nanosuccinate (highest dose) significantly reduced the progressive motility and velocity of ram spermatozoa, increased the percentage of sperm with acrosomal/head defects and seminal SOD activity, and depressed CAT (highest dose) and GPx (all doses) activity. In summary, the addition of Mn²⁺- and Zn²⁺-nanosuccinate to semen extender had beneficial effects on sperm motility/motion kinetics and structural integrity, whereas Cu²⁺-nanosuccinate generally had debilitating effects on the post-thaw semen characteristics in rams.