Effects of Different Antifreeze Protective Agents on Hu Sheep Semen Storage at 4 ˚C

The present study aimed to investigate the effects of different antifreeze protectants on the preservation of Hu sheep semen at 4 ˚C. The semen was diluted with Tris extender at room temperature, supplemented with dimethyl sulfoxide (DMSO) (0, 0.1%, 0.2%, 0.3%, 0.4% and 0.5%), glycerol (1.5%, 3.0%, 4.5% and 6.0%), glycol (2.50%, 5.00%, 7.50% and 10.00%), skimmed milk powder (SMP) (0.50%, 1.50%, 2.50% and 3.00%), soy lecithin (SL, 0.15%, 0.30%, 0.45% and 0.60%) and five optimal concentrations of antifreeze protectants (0.4% DMSO, 4.5% glycerol, 7.5% glycol, 1.5% SMP and 0.15% SL), and stored at 4 ˚C refrigerator. Spermatozoa motility parameters (spermatozoa viability, spermatozoa progressive motility, straight line velocity (VSL), curvilinear velocity (VCL) and average path velocity (VAP)) were evaluated during the preservation of semen. The addition of antifreeze protectants, especially the 0.4% DMSO, 4.5% glycerol, 7.50% glycol, 1.50% SMP and 0.15% SL exerted the best effects on spermatozoa viability and progressive motility compared to the spermatozoa without antifreeze protectants (control group). In the experiment of antifreeze protective agents with the optimal concentration, the spermatozoa viability and progressive motility of 1.5% SMP were significantly higher than those of other antifreeze groups during storage. In conclusion, the addition of 1.5% SMP to semen spermatozoa preserved at 4 ˚C refrigerator can most effectively enhance the semen preservation quality compared to the other optimal concentration of antifreeze protectant groups.