Soybean lecithin-based extender preserves spermatozoa membrane integrity and fertilizing potential during goat semen cryopreservation

Soybean lecithin may represent a suitable alternative to egg yolk for semen cryopreservation in livestock species. However, additional studies are needed to elucidate its effects on spermatozoa functional properties. Semen collected from five Sarda bucks was cryopreserved in Tris-based extender and glycerol (4% v:v) with different supplementations. In a preliminary experiment, different soybean lecithin concentrations were tested (1%-6% wt/vol) and results in terms of viability, percentages of progressive motile and rapid spermatozoa, and DNA integrity after thawing showed that the most effective concentration was 1%. In the second experiment, semen was frozen in a Tris-based extender with no supplementation (EXT), with 1% lecithin (EXT LC), and 20% egg yolk (EXT EY). The effectiveness of these extenders was also compared with a commercial extender. The EXT EY led to the highest viability and motility parameters after freezing and thawing (P<0.0001). No significant differences were observed in intracellular ATP concentrations. Additional molecular features revealed that sperm functionality was affected in EXT EY, as demonstrated by lower DNA and acrosome integrity (P<0.05), and higher lipid peroxidation compared with spermatozoa cryopreserved in EXT LC (P<0.0001). Results obtained in the heterologous invitro fertilization test showed that EXT LC better preserved spermatozoa functionality, as demonstrated by the higher fertilization rates compared with the other media (66.2±4.5% for EXT LC vs. 32.7±4.5%, 38.7±4.5%, 39.6±5.2% for EXT, EXT EY, and commercial extender; P<0.01). The present study demonstrated that lecithin can be considered as a suitable alternative to egg yolk in goat semen cryopreservation, because it ensures higher fertilization rates and a better protection from membrane damage by cold shock.