Sperm cryopreservation of silver barb (Barbodes gonionotus): cryoprotectants, cooling rate and storage time on sperm quality

Effectiveness and efficiency of frozen sperm on fertilization and hatching success of eggs from silver barb was examined in relation to cryoprotectants, freezing rate and storage period. Sperm was diluted in calcium‐free Hank's balanced salt solution, equilibrated with dimethylsulphoxide (DMSO), propylene glycol, sucrose or methanol at 5%, 10%, 15% or 20% final concentrations, and frozen in 250‐μL straws using a one‐step freezing procedure (1, 5 and 8°C min−1 from 25 to −40°C). Highest post‐thaw sperm motility was found from a treatment using 10% DMSO and 5°C min−1 (82.2 ± 2.1%), similar to that of 10% DMSO and 8°C min−1 (87.8 ± 3.2%). Post‐thaw motility of sperm frozen at 5 or 8°C min−1 was significantly higher than 1°C min−1. Relative sperm motility declined significantly after 10 months of cryostorage while viability did not change during a 12‐month cryostorage. Average fertilization rates of sperm after 1 and 4 months of storage were 64.5 ± 4.6% and 61.3 ± 3.4%, respectively, similar to those of fresh sperm (69.6–72.3%). Hatching rates of cryopreserved sperm (45.4–51.2%) were similar to those of fresh sperm (51.8–57.8%). This study developed suitable methods for cryopreservation of silver barb sperm that can be used to facilitate hatchery operation.