Efficiency of superovulation and in vivo embryo production in eFSH-treated donor mares after estrus synchronization with progesterone and estradiol-17β

T. Raz*, C. Card

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

5 Scopus citations


Reliable methods of regulating estrus and stimulating superovulations in equine embryo transfer programs are desirable. Our objectives were to investigate the efficacy of a progesterone and estradiol-17β (P&E) estrus synchronization regimen in mares with and without subsequent equine follicle-stimulating hormone (eFSH) treatment and to examine the effects of eFSH on folliculogenesis and embryo production. Cycling mares were treated with P&E daily for 10 d. On the final P&E treatment day, prostaglandin F was administered, and mares were randomly assigned to one of two treatment groups (n = 20 mares/group). In both groups, mares were examined daily by transrectal ultrasonography. In the eFSH group, twice-daily eFSH treatments were initiated at follicle diameter 20 to 25 mm and ceased at follicle ≥35 mm; human chorionic gonadotrophin (hCG) was administered after 36 h. In the control group, eFSH treatments were not given, but hCG was administered at follicle ≥35 mm. Mares were inseminated with fresh semen, and embryo recovery attempts were performed 8 d postovulation. Synchrony of ovulations within each group appeared to be similar. Six mares in the eFSH group failed to ovulate. The eFSH treatment resulted in higher (P < 0.05) numbers of preovulatory follicles and ovulations; however, embryo recovery rate did not increase (eFSH 1.0 ± 0.4 vs. control 0.95 ± 0.1 embryos/recovery attempt), and embryo per ovulation rate was significantly lower (36% vs. 73%). The eFSH-treated mares had significantly higher frequency of nonovulatory follicles (28% vs. 0) and higher periovulatory serum concentrations of estradiol-17β. Based on our findings, combined P&E and eFSH regimens cannot be recommended for cycling donor mares.

Original languageAmerican English
Pages (from-to)169-178
Number of pages10
Issue number2
StatePublished - 15 Jul 2009
Externally publishedYes

Bibliographical note

Funding Information:
This study was supported by the Equine Health Research Fund of the University of Saskatchewan. The authors thank Intervet Canada Ltd for providing Chorulon and Pharmacia Animal Health for providing Lutalyse. Special gratitude is expressed to Ms. Susan Cook from the WCVM Endocrinology Laboratory for her expertise and to Dr. Karolin Thuemler, Dr. Barb Weselowski, and Mr. Jeffrey Bergermann for technical help.


  • Embryo transfer
  • Estradiol
  • Progesterone
  • Superovulation
  • eFSH


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