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RESEARCH ARTICLE
Contents Vol 20(8)

Induction of haemorrhagic anovulatory follicles in mares

O. J. Ginther A B C , M. O. Gastal A , E. L. Gastal B , J. C. Jacob A and M. A. Beg B
+ Author Affiliations
- Author Affiliations

A Eutheria Foundation, Cross Plains, WI 53528, USA.

B Department of Pathobiological Sciences, University of Wisconsin, Madison, WI 53706, USA.

C Corresponding author. Email: ginther@svm.vetmed.wisc.edu

Reproduction, Fertility and Development 20(8) 947-954 https://doi.org/10.1071/RD08136
Submitted: 12 June 2008  Accepted: 3 August 2008   Published: 23 October 2008

Abstract

A follicular wave and luteolysis were induced in mares by ablation of follicles ≥6 mm and treatment with prostaglandin F2α (PGF) on Day 10 (where ovulation = Day 0). The incidence of haemorrhagic anovulatory follicles (HAFs) in the induced waves (20%) was greater (P < 0.007) than in preceding spontaneous waves (2%). Hormone and follicle dynamics were compared between induced follicular waves that ended in ovulations (ovulating group; n = 36) v. HAFs (HAF group; n = 9). The day of the first ovulation or the beginning of HAF formation at the end of an induced wave was designated as post-treatment Day 0. The mean 13-day interval from Day 10 (PGF and ablation) to the post-treatment ovulation was normalised into Days 10 to 16, followed by Day –6 to Day 0 relative to the post-treatment ovulation. Concentrations of LH were greater (P < 0.05) in the HAF group than in the ovulating group on Days 10, 11, 12, 14, –3 and –2. The HAF group had greater (P < 0.003) LH concentrations on Day 10 of the preceding oestrous cycle with spontaneous ovulatory waves. The diameter of the largest follicle was less (P < 0.05) in the HAF group on most days between Day 13 and Day –1 and this was attributable to later (P < 0.002) emergence of the future largest follicle at 6 mm in the HAF group (Day 12.4 ± 0.5) than in the ovulating group (Day 11.3 ± 0.1). The results indicate that the high incidence of HAFs after PGF and ablation was associated with later follicle emergence and immediate and continuing greater LH concentration after PGF treatment, apparently augmented by an inherently high pretreatment LH concentration.

Additional keywords: LH, luteinised unruptured follicle, oestradiol, prostaglandin F2α.


Acknowledgements

This study was supported by the Eutheria Foundation (Project P3-OG-08). The authors thank Pfizer Animal Health (New York, NY, USA) for the gift of Lutalyse. J. C. F. Jacob was on leave from the Department of Reproduction and Animal Evaluation, Federal Rural University of Rio de Janeiro, Rio de Janeiro, Brazil.


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