Can linoleic acid improve the quality of frozen thawed bull sperm?

BACKGROUND: Cryopreservation is known to have a detrimental effect on the motility, viability and membrane integrity of sperm cells. OBJECTIVE: The aim of this study was to investigate the effect of various amount of linoleic acid supplementation to the Tris extender, on bull sperm parameters, DNA integrity and oxidative stress after freeze-thawing. METHODS: Ejaculates were split into five aliquots and extended to a final concentration of 18x10(6) spermatozoa per ml with the base extender containing different doses of linoleic acid 0.125 ml, (L125); 0.250 ml (L250); 0.5 ml (L500), 1 ml (L1000) and no additive (control; L0). The extended samples were equilibrated slowly to 4 degree C for 4 h and then froze using a digital freezing machine. Frozen straws were thawed individually in water bath at 37 degree C for 30 s to analyse progressive motility and sperm motion characteristics as well as membrane integrity. Biochemical assays were performed in a spectrophotometer using commercial kits. DNA damage was evaluated by Comet Assay. RESULT: The addition of various linoleic acid did not improve the sperm subjective, CASA and progressive motilities, sperm motility characteristics and DNA integrity (P>0.05). L500 exhibited the greatest values for membrane integrity than that of the other groups (P<0.001). All supplementation groups led to lower percentages of tail abnormalities in comparison to the control (P<0.001). L500 and L1000 significantly decreased total abnormalities. In conclusion, our findings showed that L500 linoleic acid supplementation in semen extender was of great beneficial effect on frozen-thawed bull semen in terms of morphology and plasma membrane integrity.