Seasonal changes in ovarian activity: lessons learnt from the horse.
Abstract: The annual reproductive cycle in the horse involves a reduction in ovarian activity during short days. The absence of ovulatory activity during winter has important consequences for an equine industry eager to breed mares early during the year. The anovulatory season results from a reduction in the secretion of pituitary gonadotropin that is in turn triggered by the inhibitory effects of short photoperiod on the hypothalamus-pituitary axis. Recent studies have provided evidence that the response of the ovaries to endocrine stimuli during the anovulatory season is affected not only by circulating concentrations of trophic hormones but also by locally produced growth factors that are putative modulators of follicular responses to gonadotropins. The present review summarises current knowledge on ovarian dynamics during the equine anovulatory season and the regulatory mechanisms involved at both systemic and local levels.
Publication Date: 2006-12-15 PubMed ID: 17207590DOI: 10.1016/j.anireprosci.2006.12.001Google Scholar: Lookup
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- Journal Article
- Review
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 focuses on the annual reproductive cycle in horses, specifically how changes in daylight duration affect ovarian activity, and its implications for breeding horses earlier in the year. The study also explores the various factors (endocrine stimuli, local growth factors) that influence this process.
Understanding the Effects of Daylight on the Equine Reproductive Cycle
- The research emphasizes on how short days or reduced daylight during winter play a critical role in the annual reproductive cycle of horses. This comes into play as a reduction in ovarian activity which results in the absence of ovulation.
- This phenomenon has implications for the equine industry, particularly for breeders who wish to breed mares early in the year. With the lack of ovulatory activity in winter, this becomes a significant challenge.
Role of the Hypothalamus-Pituitary Axis
- The anovulatory season in horses is the result of a decrease in the secretion of pituitary gonadotropin, the hormones that regulate the functions of the ovaries. This reduction is triggered by the inhibitory effects of short photoperiod or reduced daylight on the hypothalamus-pituitary axis, a system that plays a key role in many functions of the body, including reproduction.
Response of the Ovaries to Various Stimuli
- Studies show that ovarian responses to endocrine stimuli during the anovulatory season are influenced not only by the circulating concentrations of trophic hormones but also by locally produced growth factors. These factors are proposed to be modifiers of follicular responses to gonadotropins, hormones that stimulate the growth and function of the ovaries.
- Therefore, the regulation of the reproductive process during the anovulatory season of horses, particularly the ovarian dynamics, is not only systemic but can also be influenced at a local level by these growth factors.
Summary of Current Research
- The article provides a concise summary of the current knowledge on the dynamics of ovarian activity during the equine anovulatory season including the regulatory mechanisms involved both at the systemic (involving the whole body or system) and the local levels.
Cite This Article
APA
Donadeu FX, Watson ED.
(2006).
Seasonal changes in ovarian activity: lessons learnt from the horse.
Anim Reprod Sci, 100(3-4), 225-242.
https://doi.org/10.1016/j.anireprosci.2006.12.001 Publication
Researcher Affiliations
- Easter Bush Veterinary Centre, Royal (Dick) School of Veterinary Studies, University of Edinburgh, Roslin, Midlothian EH25 9RG, UK. xavier.donadeu@ed.ac.uk
MeSH Terms
- Animals
- Female
- Horses / physiology
- Ovary / physiology
- Seasons
Citations
This article has been cited 6 times.- Coelho LA, Silva LA, Reway AP, Buonfiglio DDC, Andrade-Silva J, Gomes PRL, Cipolla-Neto J. Seasonal Variation of Melatonin Concentration and mRNA Expression of Melatonin-Related Genes in Developing Ovarian Follicles of Mares Kept under Natural Photoperiods in the Southern Hemisphere.. Animals (Basel) 2023 Mar 15;13(6).
- Qi Y, Xue H, Xu J, Wu M, Chen L, Xu L. Effect of PACAP/PAC1R on Follicle Development of Djungarian Hamster (Phodopus sungorus) with the Variation of Ambient Temperatures.. Biology (Basel) 2023 Feb 15;12(2).
- Kim S, Jung H, Murphy BA, Yoon M. Efficiency of Equilume light mask on the resumption of early estrous cyclicity and ovulation in Thoroughbred mares.. J Anim Sci Technol 2022 Jan;64(1):1-9.
- Segabinazzi LGTM, Andrade LRP Jr, Alvarenga MA, Dell'Aqua JA Jr, Canisso IF. Use of Intravaginal Progesterone-Releasing Device Results in Similar Pregnancy Rates and Losses to Long-Acting Progesterone to Synchronize Acyclic Embryo Recipient Mares.. Vet Sci 2021 Sep 10;8(9).
- 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.
- 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.
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