5. Conclusion
The results of this study indicate that the concentration
of EY is important for Caspian horse semen freezing,
because, when CEY at 2% concentration was added to the
1.25% soybean lecithin-based extender, a synergistic effect
between EY and lecithin provided even higher post-thaw
survival of sperm cells such as motility, morphology,
functional integrity than that of INRA0 and INRA4 during
freezing/thawing. Whereas the positive effect of INRA2 was
demonstrated on semen quality, the CEY concentration 4%
(INRA4) leads to decline of motility and membrane and
functional integrity. Additionally, the defined soybean
lecithin-based extender with centrifuged CEY 2% facilitates
motility evaluating in CASA because it has less viscous fluid.
Furthermore, the results show that freezability of Caspian
horse semen can be affected by EY concentration and type
(centrifuged versus whole). Finally, the present results
suggest that the use of a low concentration of CEY (2%) and
soybean lecithin in combination significantly improved
reproductive traits of Caspian horse semen, indicating its
beneficial effect during the freeze-thaw process. Nevertheless,
further studies should be carried out in order to
confirm with AI trials of this presented results.