Identification of Suitable Extender and Cryoprotectant for Cryopreservation Oflabeo Rohitamilt

The present study was conducted to evaluate the efficacy of different extenders and cryoprotectants for cryopreservation of Labeo rohita milt. Male brood fish (n = 5) reared at fish seed hatchery, Rawal Town Islamabad, Pakistan, were captured from different rearing ponds, and kept in hatchery ponds for acclimatization. After 6 hours, fish were injected with ovaprim at 0.2 ml/kg. After 8 h, milt was collected in a cooled sterilized falcon tube and maintained at 4 degrees C. Spermatozoa were activated and visual motility was observed. Cooled milt was diluted in experimental extenders (Alsever's solution, sugar-based extender and modified Kurokura-2 extender [KE] each with either Me2SO or methanol as cryoprotectant). Diluted milt was filled in 0.5 ml straws and frozen in liquid nitrogen vapours. Cryopreserved milt samples were thawed at 25 degrees C and assessed for fertilization rate and post-thaw sperm quality. Sperm motility, motility duration, viability and total antioxidant capacity were higher in KE with Me2SO and methanol compared with Alsever's solution and sugar-based extender. Sperm DNA integrity showed a similar trend in all treatments. Moreover, sperm fertilization rate was higher (p < 0.05) in KE + methanol compared with KE+ Me2SO. In conclusion, modified KE along with methanol as cryoprotectant proved to be the best diluent for cryopreservation of L. rohita sperm.