Effect of low-density lipoprotein addition to soybean lecithin-based extenders on bull spermatozoa following freezing-thawing - Preliminary results

Abstract

Soybean lecithin-based extenders represent an alternative to extenders containing egg yolk, but there has been discussion about their cryo-protective efficacy. Low-density lipoprotein (LDL) was proved as a cryo-protective agent, which can replace egg yolk in extenders. The aim of this study was to investigate the effects of LDL addition to the soybean extenders on their cryo-protective properties. The effect of the LDL of our production was verified using commercial egg yolk extender BULL-Xcell®, 6%, 8%, and 10% LDL (v/v) as an egg yolk replacement. The effects of LDL addition to the soybean lecithin-based extenders in concentrations of 4%, 6%, and 8% (v/v) were tested using extenders Andro Med® and Bioxcell®. In total, 64 samples from eight bulls were evaluated. Kinematic parameters of spermatozoa, resulting from Computer Assisted Sperm Analysis, and their viability, evaluated by fluorescent technique, were assessed immediately after thawing and after 2 hours. The quality of LDL compared to other studies was confirmed, and the beneficial effects of egg yolk replacement by LDL were proved in extender BULLXcell®. 8% LDL provided the best values for the majority of kinematic parameters (P < 0.05), without effect on total motility (P > 0.05). Furthermore, addition of 4%, 6%, and 8% LDL to the soybean lecithin-based extender Bioxcell® showed a positive effect on the majority of kinematic parameters of spermatozoa (P < 0.05) at both times of incubation. However there was no significant influence on total motility (P > 0.05). Viability was higher after thawing in the case of 8% LDL (P < 0.05). However, there was no consistent effect of LDL addition to the AndroMed® extender. In conclusion, cryoprotective properties of the semen extenders based on a soybean lecithin can be improved by the addition of LDL.