Low Density Lipoprotein - important player in increasing cryoprotective efficiency of soybean lecithin-based bull semen extenders.

`Imoník Ondyej,Mahásková-Postlerová Pavla,Martina Dole~Alová,`Ichtay Jiyí,Tomová Lucie,Rajmon Radko,Folková Petra,Beran Jan,Stádník Ludk

doi:10.21451/1984-3143-ar2018-0107

Abstract

Currently, considering cryopreservation of bull semen, there is no clear consensus over the comparability of cryoprotective efficacy of extenders with soybean lecithin and those based on egg yolk. The objective of this study was to prove the use of Low Density Lipoprotein (LDL) extracted from hen-egg yolk as an enhancing factor for soybean lecithin-based extenders. In total, 35 ejaculates of (seven bulls x five ejaculates per bull) were collected and cryopreserved at a commercial insemination centre. The effect of the LDL addition to the extenders AndroMed® and Bioxcell® was tested in a 6% (v/v) concentration on spermatozoa after thawing. Modified extender composition effects were assessed on sperm functional parameters motility, plasma membrane, mitochondrial membrane potential and acrosomal integrity after thawing by CASA, flow cytometry and fluorescent microscopy, respectively. Based on kinematic parameters determined from CASA, k-means cluster analysis was used to classify individual spermatozoon into specific subpopulations (fast, medium fast and slow). A subpopulation of fast spermatozoa was increased in the presence of LDL in both selected extenders (P < 0.05). Moreover, the positive effect of LDL on sperm motility was confirmed by decreasing the percentage of sperm in slow subpopulation (P < 0.05). The effect of LDL addition on the incidence of spermatozoa with intact plasma membrane was not demonstrated in any case of extender used (P > 0.05). The percentage of sperm with intact acrosome was improved when LDL was added to Bioxcell® extender (P < 0.05). On the other hand, addition of LDL to AndroMed® extender improved mitochondrial intactness after thawing (P < 0.05). In conclusion, our results showed that adding LDL to selected soybean lecithin-based extenders considerably ameliorated the functional parameters of spermatozoa after thawing and thus this lipoprotein could represent an improving agent for soybean lecithin-based extender for bull semen cryopreservation.

Highlights

Considering cryopreservation of bull semen, there is no clear consensus over the comparability of cryoprotective efficacy of extenders with soybean lecithin and those based on egg yolk
Sperm motility evaluated as a percentage of progressively motile sperm (PMOT) was not affected by Low Density Lipoprotein (LDL) addition in both extenders (P > 0.05) (Tab. 1)
Medium-fast sperm subpopulation was affected by LDL addition in both extenders (AndroMed® control: 40.3%, AndroMed® + 6% LDL 42.6, Fig. 1, P < 0.05)

Summary

Introduction

Considering cryopreservation of bull semen, there is no clear consensus over the comparability of cryoprotective efficacy of extenders with soybean lecithin and those based on egg yolk. The effect of the LDL addition to the extenders AndroMed® and Bioxcell® was tested in a 6% (v/v) concentration on spermatozoa after thawing. The effect of LDL addition on the incidence of spermatozoa with intact plasma membrane was not demonstrated in any case of extender used (P > 0.05). The percentage of sperm with intact acrosome was improved when LDL was added to Bioxcell® extender (P < 0.05). Addition of LDL to AndroMed® extender improved mitochondrial intactness after thawing (P < 0.05). Our results showed that adding LDL to selected soybean lecithinbased extenders considerably ameliorated the functional parameters of spermatozoa after thawing and this lipoprotein could represent an improving agent for soybean lecithin-based extender for bull semen cryopreservation

Objectives

Methods

Results

Discussion

Conclusion