RESUMO
In the present study, we aimed to evaluate the possible protective effects of the nicotinic acid (NA) at three concentrations (10, 20, and 40 mM) on the equine cooled and frozen-thawed spermatozoa quality markers including viability, plasma membrane or acrosome integrity, DNA fragmentation, lipid peroxidation, and total oxidant levels. We also evaluated the effects of NA on preservation of the post-thaw sperm quality after 6 hours of cold storage before freezing. Five stallions were used for semen collections. The current experiment was repeated six times using pooled semen samples from two stallions, each time. We showed that NA at 20 and 40 mM concentrations could significantly improve the stallion sperm quality markers during cold storage. However, the protective effects were not different between 20 mM and 40 mM concentrations in most measures. Nicotinic acid could also improve the post-thaw stallion sperm quality at 10, 20, and 40 mM concentrations. However, the 40 mM concentration showed a negative impact on some post-thaw kinematic sperm parameters. Nicotinic acid at 10 and 20 mM concentrations could preserve the sperm cryo-tolerance to be frozen up to 8 hours after collection without a significant decline in most of the post-thaw sperm quality measures. Nicotinic acid could also decrease the level of the lipid peroxidation and total reactive oxygen/nitrogen species in the cooled and frozen-thawed spermatozoa, in a dose-dependent manner. Therefore, NA at 20 mM concentration could preserve most of the stallion sperm quality measures during cold storage (42 hours, 5°C) and enabled storage of cooled stallion semen for 6 hours before freezing without significant deterioration of the post-thaw sperm quality.
