Follicle deviation and diurnal variation in circulating hormone concentrations in mares.
Abstract: The temporal relationships between follicle deviation and systemic hormone concentrations were studied in mares. Blood samples were obtained at 01:00, 07:00, 13:00, and 19:00 h from nine mares throughout an interovulatory interval. Diurnal variation in progesterone occurred on Days 4-12 and in LH on Days 4 and 5; the lowest concentration for both hormones was at 13:00 h. Ultrasonically observed deviation in the ovulatory follicular wave began on Day 15.7+/-0.5 (ovulation=Day 0). An increase (P<0.002) in LH began on Day 14 before the beginning of deviation, and an increase (P<0.05) in estradiol began at the beginning of deviation. Testosterone concentrations began to increase (P<0.05) 2 days after the beginning of deviation and reached maximum 1 day before the next ovulation. The beginning of deviation was encompassed by a decline (P<0.003) in cortisol concentrations, and the concentrations remained low during the preovulatory period.
Publication Date: 2006-08-30 PubMed ID: 17000062DOI: 10.1016/j.anireprosci.2006.08.025Google 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.
The research investigates the connections between the deviation of follicle development and varying levels of certain hormones in female horses. The results suggest that these hormonal changes and follicle deviation, observed through ultrasound, follow a specific temporal pattern throughout the ovulation cycle.
Study Setup
- The research involved studying hormonal variations in nine mares (female horses) during each mare’s interovulatory interval, which is the span of time between two ovulation events.
- Researchers obtained blood samples at four different times throughout the day (01:00, 07:00, 13:00, and 19:00) to consider the possibility of diurnal (daily) variations in hormone levels.
Hormone Variations and Deviation in Follicular Wave
- Two hormones, progesterone and luteinizing hormone (LH), were found to exhibit diurnal variations. Their concentration was the lowest at 13:00. This variation in progesterone and LH occurred on days 4 to 12 and days 4 and 5 respectively of the interovulatory interval.
- A noticeable shift or “deviation” occurred in the ovulatory follicular wave, which represents the development and growth of follicles that could potentially release an egg during ovulation. This deviation was observed through ultrasound starting on day 15.7 (+/-0.5).
Changes in Hormone Levels and Their Relation to Follicle Deviation
- An increase in LH began on day 14 of the cycle, before the observed follicle deviation began. This increase was statistically significant.
- The level of estradiol, one of the primary female sex hormones, began to increase at the onset of follicle deviation. This increase was also significant.
- An increase in concentrations of testosterone, traditionally considered a male hormone but also important in the female reproductive system, initiated 2 days after the beginning of follicle deviation, peaking a day before the next ovulation event.
The Role of Cortisol
- Cortisol, a hormone released in response to stress, displayed a significant decline beginning around the start of follicle deviation. Its levels remained low throughout the preovulatory period. The researchers suggest this decline may play a role in the process of deviation or the overall ovulation process.
Cite This Article
APA
Ginther OJ, Utt MD, Beg MA.
(2006).
Follicle deviation and diurnal variation in circulating hormone concentrations in mares.
Anim Reprod Sci, 100(1-2), 197-203.
https://doi.org/10.1016/j.anireprosci.2006.08.025 Publication
Researcher Affiliations
- Eutheria Foundation, Cross Plains, WI 53528, USA. ginther@svm.vetmed.wisc.edu
MeSH Terms
- Animals
- Circadian Rhythm / physiology
- Estradiol / blood
- Female
- Horses / blood
- Horses / physiology
- Hydrocortisone / blood
- Luteinizing Hormone / blood
- Ovarian Follicle / physiology
- Progesterone / blood
- Testosterone / blood
- Time Factors
Citations
This article has been cited 4 times.- Drozdzewska K, Gehlen H. Markers for internal neoplasia in the horse. Vet Med Sci 2023 Jan;9(1):132-143.
- 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.
- Satué K, Fazio E, Muñoz A, Medica P. Endocrine and Electrolyte Balances during Periovulatory Period in Cycling Mares. Animals (Basel) 2021 Feb 17;11(2).
- Samie KA, Kowalewski MP, Schuler G, Gastal GDA, Bollwein H, Scarlet D. Roles of GDF9 and BMP15 in equine follicular development: in vivo content and in vitro effects of IGF1 and cortisol on granulosa cells. BMC Vet Res 2025 Apr 27;21(1):292.
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
