Application of liposomes in sex sorting and cryopreservation of bovine semen

Standardized phospholipid liposomes are promising candidates to replace egg yolk in semen extenders. In this study liposomes were used in catch fluid (2% liposomes) during sex sorting and during cryopreservation (20% liposomes) of sorted and unsorted sperm. In a thermos‐tolerance test, compared to controls containing egg yolk, sperm quality was not diminished at 0 h and 6 h, respectively (i.e. motility: 91.6%, 86.0%; membrane integrity: 82.6%, 82.4%; morphology: 94.3%, 92.9%). Cryopreservation in extenders Sexcess® and Optixcell® containing liposomes was conducted with unsorted sperm and with spermatozoa that were sorted into the liposomes containing catch fluid. All samples were evaluated in a 6 h lasting thermo‐tolerance‐test (n = 14). Sexcess® supplemented with egg yolk resulted in a higher post‐thaw motility (56.6%, 43.8%, 37.4%), membrane integrity (52.0%, 49.1%, 50.1%) and morphology (87.1%, 78.7%, 69.3%) at 0 h, 3 h and 6 h respectively of sorted sperm cells compared to the supplementation with 20% liposomes (motility: 45.0%, 26.7%, 17.2%; membrane integrity: 30.0%, 21.2%, 28.9%; morphology: 75.3%, 68.1%, 61.4%) or Optixcell® (motility: 56.4%, 34.1%, 27.0%; membrane integrity: 33.6%, 23.6%, 25.7%; morphology: 75.3%, 67.0%, 60.1%). In case of unsorted semen, even at 6 h motility (57.9%, 44.2%, 50.2%), membrane integrity (64.9%, 38.9%, 47.2%), and morphology (85.5%, 83.1%, 83.2%) of the mentioned diluents had been on a higher quality level. In conclusion, with the chosen setup, liposomes may serve as egg yolk replacement in catch fluid during sorting but not as supplement in Sexcess® freezing extender.