The researchers wanted to see if they could improve the quality of frozen horse sperm by using different cryoprotectants instead of glycerol. They tested different combinations of sugars and amino acids in the freezing solution. They found that replacing some glycerol with urea and increasing glucose levels improved sperm quality. However, completely replacing glycerol with a mix of urea, betaine, proline, and trehalose did not work as well. This study shows that changing the cryoprotectants in the freezing solution can affect the quality of frozen horse sperm.