COMPARATIVE CHARACTERISTICS OF RAM SEMEN FROZEN IN DIFFERENT EXTENDERS
Numerous studies have proved the necessity of egg yolk in synthetic media to dilute semen before its cryopreservation. However, at the same time, it has been demonstrated that its use can adversely affect the quality of frozen-thawed sperm. The present study compares the main quality parameters of ram sperm frozen using TRIS-based diluent with egg yolk and two egg yolk-free diluents (OvixCell® and AndroMed®). A slower deterioration in the kinematic performance of sperm cryopreserved in TRIS diluent with native egg yolk confirmed higher cryoprotective performance compared to commercial extenders containing no egg yolk. Significantly higher total and progressive motility was observed in TRIS-based medium with egg yolk (P< 0.05). This advantage was maintained after four hours of incubation and became more significant at the end of cultivation (after six hours) (P< 0.01). Thus, ram sperm frozen in egg yolk medium retained better motility than in egg yolk-free extenders, which allows predicting its higher bioavailability. Assessment of some semen parameters using CASA showed that there were no significant differences in motility between the three extenders immediately after thawing the straws. When assessed two hours after thawing, a diluent containing egg yolk (TRIS-based) was found to have higher results for some of the examined traits than phospholipid diluents.