Role of diameter differences among follicles in selection of a future dominant follicle in mares.
Abstract: Follicles > or = 5 mm were ablated in pony mares by a transvaginal ultrasound-guided technique on Day 10 (ovulation = Day 0). Follicle emergence (at 15 mm, experiment 1; at 6 mm, experiment 2) and development of the new wave was monitored by transrectal ultrasound. Deviation was defined as the beginning of a marked difference in growth rates between the two largest follicles. In experiment 1, mares were grouped (n = 4 per group) into controls, ablation-controls (ablations at Day 10 only), and a two-follicle model (periodic ablation sessions so that only the two largest follicles developed). There were no significant indications that the two-follicle model altered follicle diameters, growth rates, or time intervals of the two retained follicles at or between events (follicle emergence, deviation, and ovulation). In experiment 2, the two-follicle model (n = 14) was used for follicle and hormonal characterization and hypothesis testing, without the tedious and error-prone necessity for tracking many (e.g., 20) individual follicles. The future dominant follicle emerged a mean of 1 day earlier (p < 0.008) than the future subordinate follicle, the growth rates for the two follicles between emergence and deviation (6 days later) did not differ, and the dominant follicle was larger at the beginning of deviation (23.1 +/- 0.8 mm versus 19.6 +/- 0.9 mm; p < 0.0001). Mean FSH and LH concentrations increased (p < 0.05) concomitantly from emergence of the future dominant follicle and peaked 3 days later when the follicle was a mean of 13 mm. Thereafter, the two hormones disassociated until ovulation: FSH decreased and LH increased. Results supported the hypothesis that the future dominant follicle has an early size advantage over future subordinate follicles and indicated that the advantage was present as early as 6 days before deviation.
Publication Date: 1998-01-04 PubMed ID: 9408236DOI: 10.1095/biolreprod57.6.1320Google 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
- 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.
This research investigates the factors influencing the selection of the dominant follicle in mares, particularly examining whether follicle size plays a role. The study found that the future dominant follicle often emerges earlier and grows larger than its counterparts prior to significant deviation in growth rates observed among them.
Research Methodology
- The research was conducted in two experiments. The first experiment consisted of three groups of pony mares. Follicles equal to or larger than 5mm were eliminated in these mares using a transvaginal ultrasound-guided technique on Day 10 (with ovulation counting as Day 0).
- They examined the emergence and development of new follicles using transrectal ultrasound. Deviation was defined as the point at which a clear difference in growth rates between the two largest follicles began.
- In the first experiment, the mares were divided into control groups, ablation-controls (ablations performed solely on Day 10), and the two-follicle model (where periodic ablations ensured only the two largest follicles developed).
- The second experiment used the two-follicle model for follicle and hormonal characterization, without the need for tracking several individual follicles, which can be error-prone.
Key Findings
- The research found no significant evidence that the two-follicle model influenced the diameters, growth rates, or the timing of the events of the two retained follicles.
- The results showed that the future dominant follicle typically emerges a day earlier than the future subordinate follicle. Also, the owner of these two follicles does not differ between the time they emerge and deviation, which occurs 6 days later.
- The dominant follicle was found to be larger at the start of the deviation. The mean FSH and LH concentrations increased concomitantly from the emergence of the future dominant follicle, peaking three days later when the follicle averaged 13mm.
- From this point, the two hormones exhibit a detachment until ovulation occurs, with FSH decreasing and LH increasing.
Conclusions
- The study supported the hypothesis that the future dominant follicle has an edge in size over future subordinate follicles. This size advantage was present as early as six days before deviation began.
- The findings offer significant insights for understanding follicular dynamics and could potentially influence how we manage reproduction in horse breeding.
Cite This Article
APA
Gastal EL, Gastal MO, Bergfelt DR, Ginther OJ.
(1998).
Role of diameter differences among follicles in selection of a future dominant follicle in mares.
Biol Reprod, 57(6), 1320-1327.
https://doi.org/10.1095/biolreprod57.6.1320 Publication
Researcher Affiliations
- Animal Health and Biomedical Sciences, University of Wisconsin-Madison, 53706, USA.
MeSH Terms
- Animals
- Female
- Follicle Stimulating Hormone / blood
- Horses / anatomy & histology
- Luteinizing Hormone / blood
- Ovarian Follicle / diagnostic imaging
- Ovarian Follicle / physiology
- Ovarian Follicle / surgery
- Ovulation
- Progesterone / blood
- Suction
- Ultrasonography
Citations
This article has been cited 13 times.- Gebremedhn S, Gad A, Ishak GM, Menjivar NG, Gastal MO, Feugang JM, Prochazka R, Tesfaye D, Gastal EL. Dynamics of extracellular vesicle-coupled microRNAs in equine follicular fluid associated with follicle selection and ovulation. Mol Hum Reprod 2023 Apr 3;29(4).
- Segabinazzi LGTM, Gilbert RO, Ambrosia RL, Bergfelt DR, Samper JC, Peterson EW, French HM. Structural and Functional Dynamics of the Ovary and Uterus during the Estrous Cycle in Donkeys in the Eastern Caribbean. Animals (Basel) 2022 Dec 24;13(1).
- Dutra GA, Ishak GM, Pechanova O, Pechan T, Peterson DG, Jacob JCF, Willard ST, Ryan PL, Gastal EL, Feugang JM. Seasonal variation in equine follicular fluid proteome. Reprod Biol Endocrinol 2019 Mar 6;17(1):29.
- Ishak GM, Bashir ST, Dutra GA, Gastal GDA, Gastal MO, Cavinder CA, Feugang JM, Gastal EL. In vivo antral follicle wall biopsy: a new research technique to study ovarian function at the cellular and molecular levels. Reprod Biol Endocrinol 2018 Jul 28;16(1):71.
- Alves KA, Alves BG, Gastal GD, de Tarso SG, Gastal MO, Figueiredo JR, Gambarini ML, Gastal EL. The Mare Model to Study the Effects of Ovarian Dynamics on Preantral Follicle Features. PLoS One 2016;11(2):e0149693.
- Derar RI, Hussein HA. Ovarian Follicular Dynamics during the Estrous Cycle in Jennies in Upper Egypt. Vet Med Int 2011;2011:860518.
- Lemma A, Schwartz HJ, Bekana M. Application of ultrasonography in the study of the reproductive system of tropical jennies (Equus asinus). Trop Anim Health Prod 2006 May;38(4):267-74.
- Ginther OJ, Beg MA, Gastal EL, Gastal MO, Baerwald AR, Pierson RA. Systemic concentrations of hormones during the development of follicular waves in mares and women: a comparative study. Reproduction 2005 Sep;130(3):379-88.
- Ginther OJ, Gastal EL, Gastal MO, Bergfelt DR, Baerwald AR, Pierson RA. Comparative study of the dynamics of follicular waves in mares and women. Biol Reprod 2004 Oct;71(4):1195-201.
- Feugang JM, Gad A, Menjivar NG, Ishak GM, Gebremedhn S, Gastal MO, Dlamini NH, Prochazka R, Gastal EL, Tesfaye D. Seasonal influence on miRNA expression dynamics of extracellular vesicles in equine follicular fluid. J Anim Sci Biotechnol 2024 Oct 9;15(1):137.
- Xu H, Chen Q, Tian J, Chen X, Zhang X, Li X, Wu Y, Zhang C, Zhang Y. Effect of the degree of follicular diameter ≥18mm differentiation on the day of hCG administration to the outcome of controlled ovarian hyperstimulation (COH). Front Endocrinol (Lausanne) 2024;15:1414213.
- Richard S, Zhou Y, Jasoni CL, Pankhurst MW. Ovarian follicle size or growth rate can both be determinants of ovulatory follicle selection in mice†. Biol Reprod 2024 Jan 13;110(1):130-139.
- Bashir ST, Baerwald AR, Gastal MO, Pierson RA, Gastal EL. Dominant follicle growth patterns and associated endocrine dynamics in anovulatory and ovulatory waves in women. Reprod Fertil 2023 May 1;4(2).
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
