Cryopreservation of Arctic charr, Salvelinus alpinus (L.), semen in various extenders and in three sizes of straw.

Cryopreservation of Arctic charr Salvelinus alpinus (L.) semen was investigated using three diluents, three cryoprotectants [10% dimethyl sulphoxide (DMSO), 10% dimethylacetamide (DMA) or 20% glycerol] and three sizes of straw. The three diluents and three cryoprotectants were combined, resulting in nine extenders. One part semen was added to three parts extender, and motility was evaluated to assess the toxicity of six of the extenders. Semen in nine extenders was frozen in 0.5-mL straws using liquid nitrogen vapour. Semen extended in 0.3 m glucose and each of the cryoprotectants was also frozen in 0.5-mL, 1.7-mL (flat) or 2.5-mL straws. The freezing rate in each size of straw was measured. Fertility trials were conducted to determine the post-thaw viability of the frozen semen. The motility of activated spermatozoa was higher in the DMA and DMSO extenders than in the glycerol extender. For the trial using 0.5-mL straws, post-thaw fertility results were higher for all extenders containing DMSO, or 0.3 m glucose and DMA, than for all other combinations of diluent and cryoprotectant. For the straw size comparison, the highest fertility was obtained for the 1.7-mL straw using either DMSO or DMA and for the 2.5-mL straw using DMSO. For all cryopreservation trials, fertility was low for extenders containing glycerol.