Reactive oxygen species (ROS) are generated by sperm metabolism. While, ROS are required for maturation, capacitation and acrosome reaction, they also modify many peroxidable cellular compounds. There is production of ROS during cryopreservation and frozen spermatozoa are highly sensitive to lipid peroxidation (LPO). Antioxidants exert a protective effect on the plasma membrane of frozen bovine sperm preserving both metabolic activity and cellular viability. Manganese (Mn(++)) is proved to be a chain breaking antioxidant in biological system. Therefore, we examined the role of (Mn(++)) during cryopreservation of cattle bull semen. Semen was divided into four parts and cryopreserved in egg-yolk-citrate extender + glycerol (EYC-G), EYC-G + 100 microM of Mn(++), EYC-G + 150 microM of Mn(++) and EYC-G + 200 microM of Mn(++). After four hours of cooling and 24 hrs of freezing, the spermatozoa were examined for percentage motility, Hypo-osmotic swelling (HOS), LPO and protein leakage. Addition of manganese to the semen during cryopreservation showed a protective effect and accounted for an increase in semen quality parameters [percentage motility, HOS percent and decrease in malondialdehyde (MDA) production and protein leakage]. The effect of manganese on motility and HOS was non-significant (p < 0.05) in cooled spermatozoa but significant with 150 microM of Mn(++) in frozen-thawed spermatozoa. MDA production and protein leakage decreased to a significant and maximum level (p < 0.05) on addition of 200 microM of manganese. The addition of manganese to EYC-G dilutor will improve the quality/fertility of semen, which will result in improvement of in vitro fertilization and artificial insemination success rate.
Keywords: cattle; lipid peroxidation; manganese; oxidative stress; semen.