Effect of the type of egg yolk, removal of seminal plasma and donor age on ram sperm cryopreservation

This study was conducted to assess the effect on ram sperm freezability by the replacement of traditional fresh egg yolk (FEY) with fresh clarified egg yolk (CEY) or powdered egg yolk (PEY) in extenders. Simultaneously, the effect of semen washing and donor age (1 and 2 years old) was studied on thawed sperm quality. Briefly, in two consecutives autumns, ejaculates from 8 males were collected by artificial vagina, mixed and split into two samples. One sample was washed by centrifugation and the pellet was split into three aliquots and re-suspended in an extender containing 15% of different type of egg yolk (PEY, FEY or CEY) supplemented with 5% glycerol in a Tris-based medium. The other sample was directly split into three aliquots and diluted in the same extenders. All samples were chilled for 4 h at 5°C before been frozen to -196°C. The results suggested that powdered egg yolk can be used satisfactory on ram sperm cryopreservation ensuring greater bio-security meanwhile fresh clarified egg yolk did not improve sperm freezability. Moreover, semen from 2 years old donors was more resistant to cryopreservation than semen collected from younger males. Finally, sperm washing had a beneficial effect on sperm cryosurvival.