The cryoprotective effect of low-density lipoproteins in extenders on bull spermatozoa following freezing-thawing

摘要

Egg low-density lipoprotein (LDL) was added at concentrations of 7-10% to the extenders used to freeze bull semen and its effects on the motility, mitochondria activity, acrosome integrity, membrane integrity and DNA integrity of frozen-thawed sperm were assessed. Analysis of data showed that the motility and characteristics of spermatozoa movement were higher with LDL in the extender, as compared to the extender containing 20% egg yolk. The results indicated that 8% LDL supplementation provided the highest sperm motility (55.8%) and movement characteristics (VSL, straight linear velocity: 33.8om/s; VCL, curvilinear velocity: 50.2om/s; LIN, linearity index: 56.5%; STR, mean coefficient: 76.7%; VAP, average path velocity: 35.9om/s; WOB, wobble coefficient: 63.9%). A concentration of 10% LDL resulted in a significant decline in the VSL, LIN, VAP and WOB values (P <0.05). Supplementation of LDL at 8% LDL resulted in significantly higher spermatozoa mitochondrial activity, acrosome integrity, membrane integrity and DNA integrity (P <0.05). According to all measured parameters, the extender containing 8% LDL showed beneficial cryoprotective effects on frozen-thawed bull spermatozoa. In conclusion, our results indicated that the extender containing 8% LDL extracted from egg yolk could be used successfully in the cryopreservation of bull semen with an efficacy that would be greater than present extenders containing 20% egg yolk.