Evaluation of soybean lecithin-based extenders in canine semen cryopreservation

This study aimed to evaluate the effectiveness of three concentrations of soybean lecithin-based extenders (SL) (0.5%, 0.1%, 0.05%) compared to native (homemade) egg yolk plasma (EYP) (40%) and a commercial egg yolk- based extender, 6% low-density lipoproteins (LDL) (CaniFreeze®, CF, IMV Technologies, L’Aigle, France) in the cryopreservation of canine spermatozoa. On the basis of the results of a preliminary study to optimize the preparation protocol for soybean lecithin-based media, these media underwent prolonged magnetic agitation at +4°C for up to 6 hours, followed by two cycles of microfiltration (0.22 µm). Twenty ejaculates, collected 48 hours apart from five healthy adult dogs with known fertility, were used in this study. Each ejaculate underwent an initial evaluation and was then divided among the five extenders studied (EYP 40%, CF, 0.5% SL, 0.1% SL, 0.05% SL). The diluted semen was frozen, thawed, and analyzed using the Hamilton Thorne HT-IVOS II CASA system and flow cytometer (Guava EasyCyte Plus, USA) to assess the kinetic characteristics and spermatozoa plasma membrane and acrosomal integri- ty. The data showed that the freezing medium containing 0.05% SL preserved post thaw total and progressive motility effectively, compared to the other SL-based extenders. However, the membrane and acrosomal integrity parameters remained lower compared to the control media. Therefore, SL-based extender can represent a good alternative to animal-derived membrane stabilizers if supplemented with other molecules acting synergically to protect canine sper- matozoa functional integrity. SL offers the advantage of meeting biosafety requirements in the production and use of frozen canine semen. Nevertheless, further investigations are needed to optimize the formulation and to standardize the preparation process of this cryopreservation extender.