Vitrified horse and donkey embryos did not show higher susceptibility to cell damage than those preserved by slow freezing, whether using straws or Fibreplug. However, Fibreplug with EG 7 mol/L resulted in fewer nonviable and apoptotic cells in donkey embryos. Donkey embryos showed lower susceptibility to vitrification than horse embryos. THE SUMMARY IS AVAILABLE IN SPANISH - SEE SUPPORTING INFORMATION.