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Home / Equine Research Bank / Equine Vet J / Effects of repeated embryo flushing without PGF2α admi...
Equine veterinary journal2024; doi: 10.1111/evj.14073

Effects of repeated embryo flushing without PGF2α administration on luteal function, percentage of unwanted pregnancy and subsequent fertility in mares.

Abstract: PGF is commonly given at the end of embryo flushing (EF) to shorten the interval to the next oestrus and ovulation. Objective: To determine the effect of repeated EF on plasma progesterone concentration, percentage of mares with endometritis, unwanted pregnancy and subsequent fertility in mares flushed without the use of PGF . Methods: Controlled experiments. Methods: Nine mares were inseminated in seven consecutive cycles (n = 63), to either perform an EF (n = 54) 7-9 days after ovulation or left pregnant (n = 9). PGF was not used to induce oestrus. Ultrasound examination and blood sampling were performed just before the EF and 72 h later to determine changes in progesterone concentration and signs of endometritis. Results: The overall percentage of positive EF/pregnancy was 55.5% (30/54) and 66.7% (6/9), respectively. The likelihood of pregnancy/positive EF in the first three cycles was 55.5% (15/29). This was not different (p > 0.1) from the fertility of the last four cycles (69.4%, 25/36). In five EF cycles (9.3%), mares had signs of endometritis and early luteolysis (progesterone <2 ng/mL) 72 h after EF. The reduction in progesterone concentration by 72 h after EF was greater (p < 0.05) for Day 9 (-2.3 ± 0.7 ng/mL) than Day 7 (-1.0 ± 0.8 ng/mL) or Day 8 (-1.3 ± 1.1 ng/mL) cycles. The progesterone concentration in non-flushed mares did not vary significantly during the sampled period (Day 7-12). There were 5 cycles in which the donor mare remained pregnant after the EF, although four were from a single mare. Conclusions: The mare population was limited to barren and maiden mares. The cycle order and operator allocation to each EF were not randomised. Conclusions: EF induces a subtle, but significant reduction in progesterone concentrations compared with non-EF cycles. However, the percentage of mares with EF-induced full luteolysis is low (9.3%). The fertility of mares after repeated EF without administration of PGF was unaffected; however, there is a considerable risk of unwanted pregnancy (5/27 = 18.5%) in donors from which an embryo was not recovered.
© 2024 The Authors. Equine Veterinary Journal published by John Wiley & Sons Ltd on behalf of EVJ Ltd.
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Publication Date: 2024-02-25 PubMed ID: 38403412DOI: 10.1111/evj.14073Google Scholar: Lookup
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Summary

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The research conducted an investigation on the effect of repeated embryo flushing in mares, without the use of a common drug, PGF. It focused on the impact this has on mares’ luteal function, fertility, and the risk of unwanted pregnancies.

Objective of The Research

  • This study aimed to understand the impact of repeated embryo flushing (EF) on aspects of mares’ reproduction such as the concentration of plasma progesterone, the incidence of endometritis (uterus inflammation), and unwanted pregnancies. The aim was also to determine the fertility of mares after several EF procedures carried out without administering PGF, a hormone typically used to induce oestrus (the period when mares are receptive to mating).

Methods Used

  • In this experimental study, nine mares were inseminated over seven cycles. EF was conducted 7–9 days post-ovulation for 54 cycles, while 9 cycles were kept pregnant.
  • Ultrasound examinations and blood samples were taken before the EF and 72 hours later. These tests were performed to monitor changes in progesterone levels (a hormone significant for pregnancy maintenance) and to check for signs of endometritis.

Key Findings

  • The overall rate of positive EF or pregnancy was 55.5% for the 54 EF cycles and 66.7% for the 9 pregnancy cycles. There was no significant difference in positive EF or pregnancies between the first three and last four cycles.
  • In 5 out of 54 EF cycles (9.3%), mares showed signs of endometritis and early luteolysis (the disappearance of the corpus luteum, a temporary endocrine gland involved in ovarian cycles and pregnancy) 72 hours after EF.
  • Progesterone levels dropped more on Day 9 after EF than on Day 7 or 8. Notably, the progesterone levels in mares that did not undergo EF remained constant throughout the sampled period.
  • Five cycles resulted in the donor mare remaining pregnant after EF, with four of these from the same mare.

Conclusions

  • In conclusion, this study implies that EF causes minor but significant reductions in progesterone levels compared to non-EF cycles. However, only a small percentage (9.3%) of mares undergo full luteolysis after EF.
  • The fertility rate of mares is not affected by repeated EF without administering PGF.
  • But, there is a substantial risk (18.5%) of unwanted pregnancies in donor mares from which an embryo was not recovered.

Cite This Article

APA
Martínez-Boví R, Sala-Ayala L, Querol-Paajanen A, Plaza-Dávila M, Cuervo-Arango J. (2024). Effects of repeated embryo flushing without PGF2α administration on luteal function, percentage of unwanted pregnancy and subsequent fertility in mares. Equine Vet J. https://doi.org/10.1111/evj.14073

Publication

Equine veterinary journal
ISSN: 2042-3306
NlmUniqueID: 0173320
Country: United States
Language: English

Researcher Affiliations

Martínez-Boví, Rebeca
  • Equine Fertility Group, Faculty of Veterinary Medicine, Universidad CEU Cardenal Herrera, CEU Universities, Alfara del Patriarca, Valencia, Spain.
Sala-Ayala, Laura
  • Equine Fertility Group, Faculty of Veterinary Medicine, Universidad CEU Cardenal Herrera, CEU Universities, Alfara del Patriarca, Valencia, Spain.
Querol-Paajanen, Aurora
  • Equine Fertility Group, Faculty of Veterinary Medicine, Universidad CEU Cardenal Herrera, CEU Universities, Alfara del Patriarca, Valencia, Spain.
Plaza-Dávila, María
  • Equine Fertility Group, Faculty of Veterinary Medicine, Universidad CEU Cardenal Herrera, CEU Universities, Alfara del Patriarca, Valencia, Spain.
Cuervo-Arango, Juan
  • Equine Fertility Group, Faculty of Veterinary Medicine, Universidad CEU Cardenal Herrera, CEU Universities, Alfara del Patriarca, Valencia, Spain.

Grant Funding

  • INDI-22/12 / Universidad CEU Cardenal Herrera

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