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Home / Equine Research Bank / Mol Reprod Dev / Dominant follicle and gonadotropin dynamics before ovulation...
Molecular reproduction and development2022; 89(2); 113-124; doi: 10.1002/mrd.23552

Dominant follicle and gonadotropin dynamics before ovulation in postpartum lactating mares.

Abstract: The aim of this study was to compare the dominant follicle (DF) and gonadotropin dynamics for 9 days before ovulation in postpartum lactating (PP Lactating) versus non-postpartum cycling (N-PP Cycling) mares. Every PP Lactating mare on the day of parturition was paired with a N-PP Cycling mare, and the data analyses considered the partum-ovulation interval (POI) and the postpartum interovulatory interval (PPIOI) in PP Lactating mares and two interovulatory intervals in N-PP Cycling mares. The results of the present study revealed several novel and unique aspects of DF development and FSH and LH dynamics before ovulation in PP Lactating mares when compared with N-PP Cycling mares. The most remarkable differences between both groups of mares were the following: (1) a shorter interval to ovulation in PP Lactating mares during the foal heat (POI ≤22 days) compared with all other intervals; (2) a larger DF in PP Lactating mares, and an earlier day of DF at maximum diameter during the foal heat; and (3) lower gonadotropin levels in PP Lactating mares. Regarding the particularities, PP Lactating mares had lower LH levels during the POI than the PPIOI, demonstrating a strong partum effect; spring-foaled mares had longer POIs, larger DF diameters, and lower LH levels; and lower body condition scores and higher body-weight loss led to longer POIs and smaller DF diameters in PP Lactating mares. This study contributes to a broad understanding of ovarian function in the postpartum mare.
© 2022 Wiley Periodicals LLC.
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Publication Date: 2022-01-09 PubMed ID: 35001447DOI: 10.1002/mrd.23552Google Scholar: Lookup
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  • Journal Article
  • Research Support
  • Non-U.S. Gov't

Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

The research compares ovarian and hormonal activities leading up to ovulation in mares that have given birth and are lactating, with those in mares that haven’t recently given birth or are not lactating. The results reveal differences in the development of dominant follicles and follicle stimulating and luteinizing hormone levels.

Objective of the Study

  • The goal of the research was to examine how the dynamics of the dominant follicle, which holds the egg that will be released during ovulation, as well as the dynamics of two essential reproductive hormones – follicle stimulating hormone (FSH) and luteinizing hormone (LH) – differ in the period leading up to ovulation between postpartum lactating (recently mothered and currently breastfeeding) mares and those mares that are not postpartum or lactating.

Research Methodology

  • The researchers paired each postpartum lactating mare with a non-postpartum cycling mare. They studied these pairs over a period of 9 days leading up to ovulation.
  • The two main variables considered were the period from parturition (childbirth) to ovulation (POI) and the interovulatory period following parturition (PPIOI) within the postpartum lactating mares. In the case of the non-postpartum cycling mares, two ovulation intervals were taken into account.

Findings

  • The dominant follicle development, and the levels of FSH and LH, showed significant differences before ovulation in lactating mares that had recently given birth compared with mares that were not postpartum or lactating.
  • The interval from childbirth to the first ovulation (known as “foal heat”) was shorter in postpartum lactating mares with the POI being equal to or less than 22 days.
  • The dominant follicle in postpartum lactating mares was larger, and these mares also experienced maximum dominant follicle size earlier during the “foal heat” phase.
  • Postpartum lactating mares showed lower levels of the reproductive hormones, FSH and LH, compared to non-postpartum, non-lactating mares.
  • Within the specific case of postpartum lactating mares, LH levels were lower during the period from childbirth to ovulation than they were in the interovulatory period after that, signifying a strong effect on ovulation resulting from childbirth.
  • The body condition and weight loss of the mares also had an influence. Lower body scores and higher weight loss were associated with longer periods from childbirth to ovulation and smaller dominant follicle sizes.

Significance of the Study

  • The findings from this study provide greater insight into how ovulation functions in mares after giving birth, particularly while they are still lactating. This understanding can have direct implications for breeding horses and can facilitate more successful and efficient breeding practices.

Cite This Article

APA
Gastal MO, Pastorello M, Godoi DB, Gastal EL. (2022). Dominant follicle and gonadotropin dynamics before ovulation in postpartum lactating mares. Mol Reprod Dev, 89(2), 113-124. https://doi.org/10.1002/mrd.23552

Publication

Molecular reproduction and development
ISSN: 1098-2795
NlmUniqueID: 8903333
Country: United States
Language: English
Volume: 89
Issue: 2
Pages: 113-124

Researcher Affiliations

Gastal, Melba O
  • Animal Science, School of Agricultural Sciences, Southern Illinois University, Carbondale, Illinois, USA.
  • Department of Animal Science, Federal University of Viçosa, Viçosa, Brazil.
Pastorello, Marilia
  • Animal Science, School of Agricultural Sciences, Southern Illinois University, Carbondale, Illinois, USA.
Godoi, Daniel B
  • Department of Veterinary, Federal University of Viçosa, Viçosa, Brazil.
Gastal, Eduardo L
  • Animal Science, School of Agricultural Sciences, Southern Illinois University, Carbondale, Illinois, USA.
  • Department of Veterinary, Federal University of Viçosa, Viçosa, Brazil.

MeSH Terms

  • Animals
  • Female
  • Follicle Stimulating Hormone
  • Gonadotropins
  • Horses
  • Humans
  • Lactation
  • Ovarian Follicle
  • Ovulation
  • Postpartum Period

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