Effect of low density lipoprotein on DNA integrity of freezing–thawing boar sperm by neutral comet assay

A modified protocol of neutral comet assay was utilized to assess the effect of low density lipoprotein (LDL) on the DNA integrity of boar freezing–thawing semen. The results demonstrated that the method was high sensitive and easier manipulation and LDL significantly protected sperm DNA integrity (p < 0.05) from the damage caused by cryopreservation except TD at the concentration of 6%, 7% and TM at 6%, the optimal LDL concentration in diluents was 9%. Moreover, LDL showed better protection in 0.25 ml than in 0.5 ml types of straw (p < 0.05) and no difference was observed in the same volume straw at the concentration of 9% and 10%. It was just the same for LDL effect on boar sperm DNA in cryopreservation 0 day and 30 days (p > 0.05).