Hormone profiles of mares affected by the mare reproductive loss syndrome.
Abstract: While searching for the cause of the Mare Reproductive Loss syndrome (MRLS), we postulated that 1 of 3 tissues in 40-120 D pregnant mares was the likely primary target of the noxious factor that caused early abortions: The corpora lutea (CL), the endometrium or the fetus and/or its membranes. At this stage of gestation, progesterone (P4) is solely produced by luteal tissue, eCG by endometrial cups in the endometrium and oestrogens by the feto-placental unit. We determined whether concentrations of P4, eCG and/or total conjugated oestrogens (CE) would indicate which tissue was targeted during the MRLS. P4, eCG and CE were measured in single serum samples collected from 216 mares, 60-110 D after ovulation during the 2001 MRLS outbreak. All mares had previously been confirmed pregnant by ultrasonography. The following data was obtained from each mare: Interval from ovulation, pregnancy status and normalcy of fetal fluids at the time of sampling, and pregnancy status 3 weeks after sampling and at term. There were no meaningful differences in hormone concentrations between pregnant mares that had normal and excessively echogenic fetal fluids at the time of sampling. CE were lower (p < 0.05) in mares that aborted after sample collection than in mares the carried to term. In 8 mares from which multiple samples were obtained, CE consistently decreased prior to any decreases in P4 or eCG. Arguments are presented that lead to the hypothesis that the fetal trophoblast was the primary target of the MRLS agent.
Publication Date: 2008-03-23 PubMed ID: 18363606DOI: 10.1111/j.1439-0531.2007.00955.xGoogle Scholar: Lookup
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Summary
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The research study is investigating the cause of the Mare Reproductive Loss syndrome (MRLS), theorizing that a disruption in hormone profiles targeting mainly the fetal trophoblast may lead to early abortions in mares.
Overview of the Research
- The research study is focused on Mare Reproductive Loss syndrome (MRLS), a condition that results in equine abortions. The researchers hypothesize that one of three tissues in pregnant mares may be the primary target of this condition.
- The targeted tissues are the corpora lutea (a temporary endocrine structure in female ovaries), the endometrium (the inner lining of the uterus), and the fetus or its membranes. Each of these tissues produces a specific hormone or biochemical during gestation that is necessary for pregnancy.
- The hormones of interest are progesterone (P4), which is produced by luteal tissue; equine chorionic gonadotropin (eCG), produced by endometrial cups; and conjugated oestrogens (CEs), produced by the feto-placental unit.
Research Method
- The researchers analysed the concentrations of P4, eCG, and CE to see which tissue might be targeted during MRLS. Blood samples were taken from 216 mares 60-110 days after ovulation during a 2001 MRLS outbreak.
- All mares used in the study were confirmed to be pregnant previously through ultrasonography. Data obtained from each mare included the interval from ovulation, pregnancy status, and the normalcy of fetal fluids at the time of sampling, and the pregnancy status three weeks after sampling and at term.
Research Findings
- No significant differences were found in hormone concentrations between pregnant mares that had regular and excessively echogenic fetal fluids (fluids highlighting specific tissues or body parts in an ultrasound).
- Conjugated oestrogen levels were found to be lower in mares that aborted after sampling compared to mares that carried to term, suggesting that the fetus or its membrane may be affected by MRLS.
- Multiple samples were obtained from 8 mares in which CE levels consistently decreased before any decreases in P4 or eCG.
Research Conclusion
- Based on the results of this study, the researchers suggest that the fetal trophoblast (the cells forming the outer layer of a blastocyst, providing nutrients to the embryo) might be the primary target of the MRLS agent.
- The basis for this conclusion is the observed decrease in the concentration of conjugated oestrogens, which are primarily produced by the feto-placental unit, in mares that suffered abortions.
Cite This Article
APA
Volkmann D, Zent W, Little T, Riddle T, Durenberger J, Potenza K, Sibley L, Roser J.
(2008).
Hormone profiles of mares affected by the mare reproductive loss syndrome.
Reprod Domest Anim, 43(5), 578-583.
https://doi.org/10.1111/j.1439-0531.2007.00955.x Publication
Researcher Affiliations
- Department of Veterinary Medicine & Surgery, University of Missouri, Columbia, MO 65211, USA. volkmannd@missouri.edu
MeSH Terms
- Abortion, Veterinary / blood
- Abortion, Veterinary / etiology
- Animals
- Chorionic Gonadotropin / blood
- Estrogens / blood
- Female
- Fetal Death / blood
- Fetal Death / etiology
- Horses / blood
- Horses / physiology
- Pregnancy
- Pregnancy Outcome / veterinary
- Pregnancy, Animal / blood
- Progesterone / blood
Citations
This article has been cited 1 times.- Ashraf R, Rashid S, Rasheed I, Asif S. Early embryonic death in equines and camelids. Open Vet J 2022 Nov-Dec;12(6):903-909.
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