Changes in sperm quality and lipid composition during cryopreservation of boar semen

The effect of cryopreservation on boar sperm viability, motility, lipid con tent and antioxidant enzymatic activities was studied. Three classes of sem en were determined according to a cluster analysis on the basis of the prop ortion of live and dead cells after freezing and thawing. The classes ident ified were: high (H, n = 4), average (A, n = 12) and low (L, n = 3) viabili ty. The concentration of sperm cells decreased from class H to A to L. Fres h semen samples with higher viability and a higher proportion of motile cel ls also maintained better quality after the freezing and thawing procedure. Sperm viability and motility in both fresh and thawed samples were similar in classes H and A, while significantly lower values were measured in clas s L. The relative decrease in sperm viability and motility alter cryopreser vation increased from class H to A to L. The lipid content of spermatozoa ( mug per 10(9) cells) increased significantly after freezing and thawing in classes Fl and A but not in class L. This result indicated that active sper m lipid metabolism might be responsible for the increase in lipid content. Phospholipid and triacylglycerol contents increased whereas free cholestero l content decreased after thawing. The fatty acid composition of fresh sper matozoa was similar in all three classes. The proportion of polyunsaturated fatty acids decreased significantly after freezing and thawing, indicating contamination from the diluent or peroxidation. After freezing and thawing , superoxide dismutase activity in spermatozoa was significantly higher in class L than in classes H and A, which did not differ from each other.