Cryopreservation of ram semen in extenders containing soybean lecithin as cryoprotectant and hyaluronic acid as antioxidant.

A soybean lecithin-based extender supplemented with hyaluronic acid (HA) was assayed for effectiveness to improve the quality of frozen-thawed ram semen. HA has not been tested yet in an extender containing soybean lecithin for freezing ram semen. Thus, the aim of this study was to analyse the effects of soybean lecithin at 1% or 1.5% along with HA at 0, 0.5 and 1 mg ml(-1) in a Tris-based extender on the motion characteristics, membrane integrity (HOST), viability, GSH peroxidase (GSH-PX) activity, lipid peroxidation and acrosomal status after freezing-thawing. Semen was collected from four Mehraban rams during the breeding season and frozen in the six lecithin×HA extenders. The extender containing 1.5% lecithin supplemented with no HA yielded higher total motility (52.5%±1.6), viability (55.8%±1.6) and membrane integrity (44.5%±1.7), but the effects of the lecithin concentration did not reach signification. Linearity-related parameters, ALH, BCF, lipid peroxidation, GSH-PX activity, morphology and acrosomal status were not affected by the extender composition. In general, adding HA significantly decreased sperm velocity (1 mg ml(-1) HA), total motility (only with 1.5% lecithin), viability (1 mg ml(-1) HA for 1% lecithin; both concentrations for 1.5% lecithin) and membrane integrity. In conclusion, adding HA to the freezing extender supplemented with soybean lecithin failed to improve quality-related variables in ram semen. Increasing the lecithin content could have a positive effect, but further studies are needed.