Cryostorage of silver barb (Barbodes gonionotus) semen in dry shipper: Efficacy, risk of bacterial cross-contamination and effects of Aeromonas hydrophila on post-thaw sperm quality

Abstract

This study was conducted to investigate the efficacy of dry shipper for the cryostorage of silver barb (Barbodes gonionotus) sperm, the subsequent risk of bacterial cross-contamination, and the effects of Aeromonas hydrophila on post-thaw sperm. Semen was diluted with calcium-free Hank's balanced salt solution containing 10% ME2SO, frozen at −8 °C/min and stored for 14 d in a dry shipper. A significant decline (P < 0.05) in the post-thaw sperm motility and viability of samples kept in the dry shipper for 14 d showed a reverse correlation (P < 0.05) with a slight increase in temperature within the dry shipper. The levels of contaminated bacteria in the compartments of the dry shipper were significantly (P < 0.05) lower than those detected in the liquid nitrogen tank. Bacteria from the atmosphere could recontaminate the chambers of the dry shipper and liquid nitrogen tank after 14 d. Bacillus was the most common bacteria isolated from the dry shipper, liquid nitrogen tank, circulating air, bench surface and outer surface of straws. There was no cross-contamination of A. hydrophila from contaminated straws to pathogen-free straws kept in either cryogenic tank. Post-thaw sperm motility and sperm viability significantly (P < 0.05) declined during cryostorage in the dry shipper and liquid nitrogen tank due to the introduction of A. hydrophila and the interaction effect of A. hydrophila and freezing. This study reports, for the first time, the efficacy of a dry shipper for the cryostorage of fish sperm for at least 14 d without a risk of bacterial cross-contamination.