The effect of three different hormonal protocols to prepare anestrous recipient mares on embryo survival was evaluated. The first group consisted of only progesterone administration (NE) 4 days before embryo transfer, while the recipients from the other two groups received a single administration of 2.5 mg of oestradiol benzoate (SE) 2 days earlier or 8 mg of oestradiol split in increasing doses for 5 consecutive days (LE) ending 3 days before progesterone treatment. The likelihood of recovering an embryo 2 days after transfer was 46.1% (6/13), 62.5% (5/8) and 85.7% (6/7) for recipient mares from the no oestrus, short and long oestrous groups respectively (p = .09). In conclusion, the presence and duration of oestradiol treatment before progesterone administration tended to influence the embryo survival in anestrous recipients 2 days after transfer. The surviving embryos recovered from the three different groups of recipients did not show any difference in size and morphology.
Keywords: anestrous recipient; embryo transfer; mare; oestradiol treatment.
© 2022 The Authors. Reproduction in Domestic Animals published by Wiley-VCH GmbH.