Cryopreservation of spermatozoa of Mrigal, Cirrhinus cirrhosus with a view to minimize inbreeding and hybridization

To develop and standardize the cryopreservation protocol of C. cirrhosus sperm, a series of experiments were conducted. Seven extenders, egg-yolk citrate, urea egg-yolk, 0.9% NaCl, Kurokura-2, Ma and Mb and four cryoprotectants viz. DMSO, glycerol, methanol and ethanol were used to find out the suitable cryodiluent. Among the cryodiluents egg-yolk citrate with DMSO yielded (mean±SD) highest post-thaw motility (83%±5.70) that was closely followed by egg-yolk citrate with methanol (81%±6.51) and urea egg-yolk with DMSO (79%±6.47). Six dilution ratios such as 1: 2, 1: 4, 1: 7, 1: 10, 1: 15, and 1: 20 (milt:cryodiluent) were used to determine the suitable milt dilution and found that sperm motility percentage increased roughly with the increase of dilution ratio. Different dilution ratios exhibited marked differences in the post-thaw spermatozoan motility (P=0.000) and revealed that it has an interaction effect with the extenders (P0.05). To determine the optimal cryoprotectant concentration, an increasing series of cryoprotectant concentrations from 5 to 30% (v/v) were tested. DMSO at 10% concentration produced averagely highest post-thaw motility with all three extenders. Methanol and ethanol produced best result at 10% concentration but their lower (20%) concentrations decreased spermatozoan motility