Follicle diameters and hormone concentrations in the development of single versus double ovulations in mares.
Abstract: Relationships between double ovulations and plasma hormone concentrations were compared between 18 single ovulating and 6 double ovulating mares. The study began when the first follicle reached >or=30 mm, and ultrasound scanning and blood sampling were done every 12h to Day 3 (ovulation=Day 0). Data were analyzed for 2.5 d after the largest follicle was >or=30 mm and after Day -2.5 to encompass the mean 5-d interval between a >or=30 mm follicle and Day 0. During the 2.5 d after >or=30 mm, the increasing diameter of the largest follicle was less pronounced and plasma FSH concentrations were lower (approached significance) in the double ovulators than in the single ovulators. By Day -2.5, the largest follicle was smaller (P<0.01) and plasma FSH was lower (P<0.04) in the double ovulators. Plasma estradiol concentrations were higher (Por=30 mm in the double ovulators and the correlation between estradiol and FSH was negative (r=-0.39, P<0.0001). In double ovulators, compared to single ovulators, the largest follicle was smaller, FSH was lower and estradiol was higher on most occasions between Days -2.5 and -0.5 (P<0.05), but plasma concentrations of LH and ir-inhibin were not significantly different. In conclusion, smaller preovulatory follicles in double ovulators were a response to lower FSH concentrations, due to higher estradiol concentrations from two preovulatory follicles; preovulatory differences in hormone concentrations between single and double ovulators were an effect rather than a cause of the double ovulations.
Publication Date: 2008-02-01 PubMed ID: 18242675DOI: 10.1016/j.theriogenology.2007.11.004Google Scholar: Lookup
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 compares hormone levels and follicle sizes in horses that ovulate once or twice during their menstrual cycle. It found that horses with two ovulations had smaller preovulatory follicles and lower levels of a hormone called FSH, due to higher estradiol levels.
Methodology and Study Design
- The study examined the relationship between double ovulations and plasma hormone concentrations, using similar observations from 18 single ovulating and 6 double ovulating mares.
- The researchers commenced the study when the first follicle reached a diameter equal to or over 30mm. To collect data, they performed ultrasound scans and took blood samples every 12 hours until Day 3, with Day 0 marked as the ovulation day.
- The study data was analyzed for two periods: 2.5 days after the largest follicle reached equal to or over 30mm, and from Day -2.5 to Day 0, a span that covers the mean five-day interval between the emergence of a 30mm follicle and ovulation.
Analysis and Findings
- In the 2.5 days after the largest follicle reached equal to or greater than 30mm, the diameter growth of the largest follicle in double ovulating mares was less significant, and plasma FSH concentrations were lower compared to those in single ovulating mares.
- By Day -2.5, the double ovulating mares had a smaller largest follicle and lower FSH concentrations compared to single ovulating mares.
- Between Day -2.5 and -0.5 in most cases, double ovulating horses showed smaller largest follicles, lower FSH, and higher estradiol.
- However, there was no significant difference in the plasma concentrations of LH (luteinizing hormone) and ir-inhibin between the two groups.
- The study revealed that the smaller sizes of preovulatory follicles in double ovulators were a response to lower FSH concentrations, which were caused by higher estradiol concentrations from two preovulatory follicles.
Conclusion
- The final inference of the study is that the differences in hormone concentrations between single and double ovulating mares are the result of the double ovulation, rather than the cause for the same.
Cite This Article
APA
Ginther OJ, Gastal EL, Rodrigues BL, Gastal MO, Beg MA.
(2008).
Follicle diameters and hormone concentrations in the development of single versus double ovulations in mares.
Theriogenology, 69(5), 583-590.
https://doi.org/10.1016/j.theriogenology.2007.11.004 Publication
Researcher Affiliations
- Eutheria Foundation, Cross Plains, WI 53528, USA. ginther@svm.vetmed.wisc.edu
MeSH Terms
- Animals
- Estradiol / blood
- Female
- Follicle Stimulating Hormone / blood
- Horses / blood
- Horses / physiology
- Luteinizing Hormone / blood
- Ovarian Follicle / physiology
- Ovulation / physiology
- Statistics, Nonparametric
Citations
This article has been cited 1 times.- Rosa LC, Dias ECS, Melo RS, do Rosário CJRM, Pereira FLC, Chung LBO, da Anunciação ARA, Moraes FJ, Souza FA, Chaves RM. The ovarian and uterine responses of Baixadeiro mares to prostaglandin synchronization during the dry and rainy seasons. Anim Reprod 2022;19(1):e20200050.
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
