COMPARISON BETWEEN RAPID AND SLOW CRYOPRESERVATION PROTOCOLS FOR RAM SEMEN

Information regarding adequate freezing protocols of ram semen considering freezing distance and time during cryopreservation has not been adequately reported. Therefore, this study aimed to compare two freezing protocols for Najdi ram's semen. In the rapid freezing protocol, the straws were frozen at 5 cm over the surface of liquid nitrogen for 15 minutes. While in the slow freezing protocol, the straws were frozen at 8 cm over the surface of liquid nitrogen for 20 minutes. The semen was collected from five rams and extended with tris egg yolk glycerol cryodiluent. The extended semen was chilled slowly to 50C within two hours and equilibrated for two hours before being frozen on the liquid nitrogen vapor and cryopreserved at -1960C. There was no significant (P >0.005) effect of the freezing protocol on the sperm’s total motility, plasma membrane integrity, DNA integrity, and abnormalities. However, the vitality, fast progressive motility, straight-line velocity, average pathway velocity, linearity, and wobble were significantly higher in rapid freezing than in slow freezing protocol. In conclusion, cryopreservation of ram semen using rapid freezing (5 cm for 15 mins) protocol was better than slow freezing (8 cm for 20 mins) protocol regarding post-thawing semen quality. Key words: freezing protocol; cryopreservation; egg yolk; ram; semen