Effect of different sperm concentrations on the post-thaw viability and motility of turkey spermatozoa cryopreserved by the pellet method

The effects of different prefreezing semen concentrations on post-thawing quality of turkey semen cryopreserved with the pellet method were investigated. Ten pooled semen samples were each divided into 6 subsamples and diluted with Tselutin extender to obtain a final concentration of 0.5, 1, 2, 3, 4 and 5x109/mL respectively. Subsamples were cooled, added with 8% of dimethylacetamide as cryoprotectant and, after 5 minutes of equilibration, seminal aliquots of 80 μL were directly dropped into a liquid nitrogen bath to form frozen pellets. Thawing was performed in few seconds at 75°C. Sperm motility (Accudenz® swim-down test), viability (SyBr-Propidium Iodide staining) and sperm susceptibility to osmotic stress (Hyposmotic-water test) were assessed. Cryopreservation caused an overall loss of sperm quality, however differences in seminal parameters due to the different sperm concentration were observed in turkey spermatozoa after thawing: spermatozoa diluted to 4x109/mL showed significant higher values in mobility, viable and osmotic resistant spermatozoa compared to the other concentrations. This study showed that the post-thaw quality of turkey semen cryopreserved by pellets method was affected differently in relation to prefreezing sperm concentration.