Experiments were conducted concerning cryoprotectants, extenders, and post thawing activating solutions for the semen of Nile tilapia Oreochromis niloticus, var. Chitralada. The extender solutions contained DMSO or methanol in various concentrations. The semen was previously diluted in the extender, drawn into 0.5 mL straws, frozen in the cryogenic shipper and then stored in liquid nitrogen. Motility of the thawed sperm was evaluated with NaHCO3 119mM, NaCl 25 mM and distilled water. Motility rate of thawed sperm, cryopreserved with methanol (final concentration = 7.5-12%) and activated with NaHCO3 119mM, was 31-46%. When DMSO replaced methanol, the motility of frozen/thawed sperm activated, also with NaHCO3 119mM, was 20-35%. Semen:extender dilutions of 1:1 to 1:4 did not show significant effects on the post-thawing sperm motility rate.
sperm cryopreservation; cryoprotectants; semen dilution rate; sperm motility rate; Nile tilapia
