A comparative study: Efficacy of boiled egg yolk vs fresh egg yolk and soy lecithin against cryodamage in Dalagh ram spermatozoa

Finding a decent alternative for egg yolk is of great importance because it has some limitations. Thus, the effectiveness of 1.5 and 3% of boiled egg yolk (BEY1.5 and BEY3) were compared to 20% of fresh egg yolk (FEY20) and 1.5% of lecithin (Lec1.5) on the cryopreservation of ram sperm. Semen samples of healthy Dalagh rams (n = 3) were collected, pooled and extended in a 1:20 ratio after being qualified. They were then subjected to 2 h incubation in a fridge and packed in straws. Straws were exposed to nitrogen vapour for 10 min and then plunged into liquid nitrogen. Sperm kinematic parameters, membrane integrity, abnormality, apoptotic rate, viability and mitochondrial activity were assessed after thawing. According to the results, sperm total and progressive motility and plasma membrane integrity were significantly higher in BEY3 and FEY20 compared to other treated groups (P < 0.05). In addition, BEY3 and FEY20 had significantly higher straightness, lateral head displacement, linearity, straight-line velocity and average path velocity compared to the BEY1.5 group. The highest viability (53.9%) and dead sperm percentage (31.6%) were recorded in the FEY20 and BEY1.5 treatments. In addition, FEY20 and BEY3 had the lowest apoptotic rate (27.60 and 23.13 vs 33.56%) and the highest mitochondrial activity (47.66 and 49.00 vs 40.00%) compared to the Lec1.5 group. The abnormality rate, however, was not significantly affected by treatments. In summary, broiled egg yolk could be a decent alternative for fresh egg yolk or lecithin in ram sperm cryo-extender.