Kinematic Response of Buck Sperm to Low-density Lipoproteins in Fresh Diluted, Short Term and Long Term Stored Semen

The present study was designed to evaluate kinematic response of sperm cell to low-density lipoproteins (LDL) in fresh diluted, short-term (4°C) or long-term (-196°C) stored semen. Four healthy bucks of similar age and weight were selected as semen donor. The semen was collected twice a week using artificial vagina. The semen after initial evaluation was pooled and divided into three aliquots, each diluted with TRIS based extender containing 8% LDL to reach final concentration of 200 million sperm/ ml. The first aliquot was evaluated after 15 to 20 minutes of its storage at 37 °C, second after it storage at 4°C for 48 hours and third was cryopreserved and evaluated after seven days of storage. Percent live sperm, sperm responsive to hypo osmotic swelling test and those exhibiting rapid progression were significantly (P ≤ 0.01) higher in fresh diluted followed by short and long term sored semen. A significant (P ≤ 0.01) decrease in the kinematic characters (average path velocity (VAP, μm/sec), straight line velocity (VSL, μm/sec), Linearty (Lin%), Straightness (Str %), Wobble (WOB%), beat cross frequency (BCF %) and maximum amplitude-lateral head displacement (ALH, μm) was observed in short term followed by long term store semen as compared to fresh diluted semen. Low-density lipoprotein was able to maintain the curvilinear velocity (VCL, μm/sec) of sperm subjected to 4°C during short term storage. In conclusion, decrease in temperature during semen storage alter the sperm path and its velocities, but LDL has a protective effect on sperm flagellar assembly and mitochondrial energy production system that sustained the sperm capacity to travel total distance per unit time upto 4°C during short term storage.