Effect of different thawing temperatures on the viability, in vitro fertilizing capacity and chromatin condensation of frozen boar semen packaged in 5 ml straws

The effect of two different thawing temperatures on frozen boar semen viability, in vitro fertilizing capacity and chromatin condensation and stability was studied. Freeze-thaw motility, normal apical ridge (NAR), in vitro fertilizing (IVF) capacity and chromatin condensation and stability were evaluated after thawing at 42 °C, 40 s and 50 °C, 40 s. Chromatin condensation degree was determined by flow cytometry, using propidium iodide as fluorochrome intercalating agent, and chromatin stability was evaluated by the same procedure after inducing sperm chromatin decondensation with ethylene diamine tetraacetic acid (EDTA) and sodium dodecyl sulfate (SDS). The results showed that thawing straws at 42 °C, 40 s significantly reduced motility compared to straws thawed at 50 °C, 40 s. NAR, penetration, monospermy and polyspermy were not different between the two groups of samples thawed at different temperatures. Chromatin was significantly more compact when thawing was performed at 50 °C, but its stability did not show any difference relative to thawing at 42 °C. It is suggested that the interactions involved in chromatin overcondensation had a non-covalent nature.