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

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 lecithinbased 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.

Contributions of seminal plasma proteins to fertilizing ability of bull sperm: A meta‐analytical review

“…The misconfiguration of lipids disrupts the interaction between sperm membrane and proteins, which interfere with the action(s) of seminal proteins on cryopreserved sperm cells (Leahy & de Graaf, 2012). Cryoinjuries in sperm membranes may be reduced by adding cholesterol, low‐density lipoproteins, and alternative sources of phospholipids to extenders rather than proteins (Neves et al, 2014; Ondřej et al, 2019; Silva et al, 2014). Authors postulated that the seminal plasma contains potential biomarkers of sperm freezability, such as clusterin, acidic seminal fluid protein, OPN, BSP1, BSP5, deoxyribonuclease 1 like 3, and seminal RNase (Gomes et al, 2020; Jobim et al, 2004; Magalhães et al, 2016; Rego et al, 2016).…”

Semen extenders: An evaluative overview of preservative mechanisms of semen and semen extenders

“…According to several studies, egg yolk can be used with a 20% extender concentration [24,82,90]. In contrast, LDL can be used with 8% concentration [91,92], and 2% LDL can be added solely with skimmed milk [10,89]. One significant challenge of using egg yolk and its derivatives is microbial contamination by Escherichia coli.…”

Comparison of different poultry egg yolks-citrate extender with green tea (Camellia sinensis) extract addition on Sapudi ram spermatozoa quality in chilled temperature storage

“…Egg yolk-based extender is often used for semen preservation. Lipoproteins and lecithin in egg yolk played a role in maintaining the integrity of the spermatozoa plasma membrane (Ondřej et al, 2019) and PMI was crucial in the fertilization process that determines the success of AI (Wurlina et al, 2020). A previous study reported that chickens, quail, and duck's egg yolks were helpful as an extender in Pelung rooster semen (Widiastuti et al, 2018).…”