Oestrogen pattern during early pregnancy in the mare.
Abstract: Plasma total (conjugated + unconjugated) oestrogens were measured from Day 0 to 100 of pregnancy and compared with the levels found during the oestrous cycle. From Day 0 to 35 of gestation, the concentrations were similar to those during dioestrus. An increase in total oestrogens between Days 35 and 40 was followed by a plateau of 3 ng/ml between Days 40 and 60 which was slightly higher than preovulatory concentrations. This first increase in total oestrogen level was produced by the ovaries since values were suppressed after ovariectomy; stimulation may be due indirectly to PMSG causing follicular growth. After Day 60, a second increase was detected and considered to be of feto-placental origin as the levels at this time were not suppressed after ovariectomy. By Day 85, oestrogen concentrations exceeded thos detected in non-pregnant mares so that a direct measurement of total oestrogens in plasma by a simplified radioimmunoassay after Day 85 of gestation offers a reliable method of pregnancy diagnosis.
Publication Date: 1979-01-01 PubMed ID: 289820
The Equine Research Bank provides access to a large database of publicly available scientific literature. Inclusion in the Research Bank does not imply endorsement of study methods or findings by Mad Barn.
- Journal Article
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 article deals with the fluctuating levels of oestrogens (a female sex hormone) in mares during the initial 100 days of their pregnancy. It reveals that total estrogen levels can be indicative of the pregnancy status and be used as a reliable diagnostic tool post the 85th day.
Methodology
- The scientists measured the total oestrogens – which include both conjugated (joined) and unconjugated hormones – in the plasma of pregnant mares from the first day up to the 100th day.
- These measurements were then compared with levels of oestrogens during the oestrous cycle. The oestrous cycle is a reproductive cycle in female mammals, including mares, and is comparable to the menstrual cycle in humans.
Findings and Interpretations
- From the start of gestation until around Day 35, the oestrogen concentrations were found to be similar to those levels during dioestrus (a phase of the oestrous cycle).
- Between Days 35 and 40, an increase in total oestrogens was observed, followed by a plateau or stabilizing phase at 3 ng/ml from Day 40 to 60. This was slightly higher than the oestrogen concentrations before ovulation.
- The initial increase in oestrogen levels was likely produced by the ovaries, as demonstrated by the oestrogen values being suppressed after an ovariectomy (the surgical removal of one or both ovaries). The researchers suggest that the stimulation of this increase could be indirectly due to PMSG (Pregnant mare’s serum gonadotropin), which causes follicular growth.
- After Day 60, a second increase in oestrogen levels was detected. The paper contends this increase to be linked to the fetus and the placenta, as oestrogen levels at this point were not affected by ovariectomy.
- By the 85th day, oestrogen levels exceeded those detected in non-pregnant mares suggesting that total oestrogen levels can act as a reliable indicator of pregnancy after the 85th day. The paper advocates using a simplified version of the radioimmunoassay (a laboratory method for measuring substances in the blood) to confirm pregnancy after Day 85.
Implications
- The findings of this study offer a new, reliable means of diagnosing pregnancy in mares beyond the 85th day of gestation based on the total oestrogen levels in plasma.
- This insight can greatly assist breeders, veterinarians, and scientists in managing equine health and reproduction.
Cite This Article
APA
Terqui M, Palmer E.
(1979).
Oestrogen pattern during early pregnancy in the mare.
J Reprod Fertil Suppl(27), 441-446.
Publication
Researcher Affiliations
MeSH Terms
- Animals
- Castration
- Estrogens / blood
- Estrus
- Female
- Horses / physiology
- Ovulation
- Pregnancy
- Pregnancy, Animal
- Progesterone / blood
- Time Factors
Citations
This article has been cited 3 times.- Haneda S, Dini P, Esteller-Vico A, Scoggin KE, Squires EL, Troedsson MH, Daels P, Nambo Y, Ball BA. Estrogens Regulate Placental Angiogenesis in Horses.. Int J Mol Sci 2021 Nov 9;22(22).
- Durward-Akhurst SA, Schultz NE, Norton EM, Rendahl AK, Besselink H, Behnisch PA, Brouwer A, Geor RJ, Mickelson JR, McCue ME. Associations between endocrine disrupting chemicals and equine metabolic syndrome phenotypes.. Chemosphere 2019 Mar;218:652-661.
- Antczak DF, de Mestre AM, Wilsher S, Allen WR. The equine endometrial cup reaction: a fetomaternal signal of significance.. Annu Rev Anim Biosci 2013 Jan;1:419-42.
Use Nutrition Calculator
Check if your horse's diet meets their nutrition requirements with our easy-to-use tool Check your horse's diet with our easy-to-use tool
Talk to a Nutritionist
Discuss your horse's feeding plan with our experts over a free phone consultation Discuss your horse's diet over a phone consultation
Submit Diet Evaluation
Get a customized feeding plan for your horse formulated by our equine nutritionists Get a custom feeding plan formulated by our nutritionists
