Effect of Glycerol on Fertility of Cryopreserved Grass Carp (Ctenopharyngodon idella) Sperm

Abstract

This research investigated the effect of adding glycerol to different ionic extenders on motility and fertilizing ability of frozen-thawed sperm of grass carp (Ctenopharyngodon idella) under hatchery conditions. Semen was collected by abdominal stripping from adult males and diluted to a ratio of 1:3 in Kurokura I or Kurokura II extender containing 10%, 15%, or 20% glycerol. Diluted semen was packaged in 0.5-ml straws and left to equilibrate for 30 min at 4°C. Following equilibration, the straws were exposed to liquid nitrogen vapor for 10 min and plunged into liquid nitrogen (-196°C). Straws were thawed in a water bath at 30°C for 10 s to determine the post-thaw motility and movement duration. The spermatozoa:egg ratio in fertilization experiments was 1 x 105:1. The highest mean fertilization rate (95.63±0.52; p>0.05) was obtained with semen frozen in Kurokura I extender containing 10% glycerol. Results indicate that grass carp sperm can be successfully cryopreserved with ionic extenders containing glycerol at 10-20%.