The researchers wanted to improve the process of freezing donkey sperm by testing different factors like sugar levels, sperm concentration, volume, and storage containers. They found that using an extender with egg-yolk and 0.1 M sugar resulted in better sperm quality after freezing. Sperm concentration didn't make a difference in the freezing process. Using smaller straws with covers was better for preserving sperm quality compared to larger straws. Overall, freezing donkey sperm in an extender with egg-yolk and 0.1 M sugar, at a concentration of 300 million sperm/mL in 0.25 mL straws with covers gave the best results.