The influence of age, antral follicle count and diestrous ovulations on estrous cycle characteristics of mares.
Abstract: Reproductive aging must be well understood to optimize the reproductive management of older mares and to predict their reproductive life-span. The objectives of this study were to: 1) examine age-related differences in follicular dynamics, endocrine profiles, and primordial follicle counts, 2) evaluate the influence of antral follicle count (AFC) on age-related changes in follicular parameters, and 3) determine the influence of diestrous ovulations on the estrous cycle. Young (3-8yr; n = 10), middle-aged (9-18 yr; n = 16), and old (>18 yr; n = 19) light horse mares were examined with transrectal ultrasonography to monitor follicular growth over two consecutive estrous cycles. Jugular blood samples were taken and plasma progesterone and FSH concentrations were determined by an enzyme immunoassay and radioimmunoassay, respectively. Both interovulatory intervals and follicular phases were longer and the day of follicle deviation occurred later in aged mares. Furthermore, older mares had a tendency to ovulate smaller follicles. Neither follicular growth rate, the number of ovulations nor the length of luteal phase was influenced by mare age. Interestingly, as mare age increased, mares with low AFC had longer interovulatory intervals and follicular phases than mares with medium or high AFC. In addition, the number of primordial follicles declined with an increase in mare age but varied considerably between mares of the same age. Progesterone concentrations were positively influenced by age, whereas FSH concentrations were not, despite that FSH concentrations appeared higher in aged mares during the follicular phase. Estrous cycles with a diestrous ovulation had a longer interovulatory interval as well as a longer follicular and luteal phase while day of deviation occurred later. Progesterone concentrations were significantly higher on day 14 and 16 in estrous cycles with a diestrous ovulation than without a diestrous ovulation. In conclusion, aging in mares is associated with changes in follicular parameters which in turn are closely linked to differences in antral follicle count suggesting a relationship with ovarian reserve. Therefore, determination of antral follicle counts in aged mares can provide valuable information about the reproductive aging process. Finally, diestrous ovulations have a significant influence on different estrous cycle parameters.
Copyright © 2017 Elsevier Inc. All rights reserved.
Publication Date: 2017-04-13 PubMed ID: 28583606DOI: 10.1016/j.theriogenology.2017.04.019Google Scholar: Lookup
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- Journal Article
Summary
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This research explores how age, follicle count and ovulations in the non-estrous period can impact a mare’s reproductive cycle. It found that as mares age, changes in their follicular parameters, influenced by antral follicle count, contribute to their reproductive aging process. Additionally, ovulations that occur outside of the normal estrous cycle can significantly influence various parameters of the estrous cycle.
Objective and Methodology
- This study aimed to understand the reproductive ageing in mares and to provide insights into predicting their reproductive lifespan.
- The researchers focused on studying the impact of age-induced changes in follicular dynamics, endocrine profiles and primordial follicle counts.
- They also sought to understand the influence of antral follicle count on these age-related changes.
- Lastly, they examined the effect diestrous ovulations have on the estrous cycle.
- Mares of varying ages (young, middle-aged, and old) were observed over two consecutive estrous cycles using transrectal ultrasonography.
- Progesterone and FSH concentrations in their blood were measured to evaluate endocrine profiles.
Key Findings
- The study found that with increasing age, the period between ovulations and the follicular phases becomes longer.
- Older mares also tend to have smaller ovulating follicles.
- However, age did not influence the speed of follicular growth, the number of ovulations, or the length of the luteal phase (post-ovulation period).
- The number of primordial follicles decreased with age, and this could vary significantly between mares of the same age.
- Progesterone concentrations increased with age, but FSH concentrations remained unchanged. However, FSH concentrations seemed to increase during the follicular phase in older mares.
- Mares with a lower count of antral follicles had longer periods between ovulations and longer follicular phases as their age increased.
- Non-estrous cycle ovulations lead to longer periods between ovulations, follicular and luteal phases.
Conclusion
- The researchers concluded that the ageing in mares is closely tied to changes in follicular parameters, which the study suggests is linked to the antral follicle count or ovarian reserve.
- By determining the antral follicle counts in aged mares, a better understanding of their reproductive aging process can be achieved.
- Diestrous ovulations also considerably influence different parameters of the estrous cycle.
Cite This Article
APA
Claes A, Ball BA, Scoggin KE, Roser JF, Woodward EM, Davolli GM, Squires EL, Troedsson MHT.
(2017).
The influence of age, antral follicle count and diestrous ovulations on estrous cycle characteristics of mares.
Theriogenology, 97, 34-40.
https://doi.org/10.1016/j.theriogenology.2017.04.019 Publication
Researcher Affiliations
- Department of Veterinary Science, Gluck Equine Research Center, University of Kentucky, Lexington, KY, 40546-0099, USA.
- Department of Veterinary Science, Gluck Equine Research Center, University of Kentucky, Lexington, KY, 40546-0099, USA. Electronic address: b.a.ball@uky.edu.
- Department of Veterinary Science, Gluck Equine Research Center, University of Kentucky, Lexington, KY, 40546-0099, USA.
- Department of Animal Science, University of California, Davis, CA, 95616, USA.
- Department of Veterinary Science, Gluck Equine Research Center, University of Kentucky, Lexington, KY, 40546-0099, USA.
- Department of Veterinary Science, Gluck Equine Research Center, University of Kentucky, Lexington, KY, 40546-0099, USA.
- Department of Veterinary Science, Gluck Equine Research Center, University of Kentucky, Lexington, KY, 40546-0099, USA.
- Department of Veterinary Science, Gluck Equine Research Center, University of Kentucky, Lexington, KY, 40546-0099, USA.
MeSH Terms
- Aging / physiology
- Animals
- Estrous Cycle / physiology
- Female
- Horses / physiology
- Ovarian Follicle / physiology
- Ovulation / physiology
Citations
This article has been cited 3 times.- Mainguy-Seers S, Diaw M, Lavoie JP. Lung Function Variation during the Estrus Cycle of Mares Affected by Severe Asthma. Animals (Basel) 2022 Feb 17;12(4).
- Requena F, Campos MJAPM, Martínez Marín AL, Camacho R, Giráldez-Pérez RM, Agüera EI. Assessment of Age Effects on Ovarian Hemodynamics Using Doppler Ultrasound and Progesterone Concentrations in Cycling Spanish Purebred Mares. Animals (Basel) 2021 Aug 8;11(8).
- Khan IU, Khairullah AR, Khan AY, Rehman AU, Mustofa I. Strategic approaches to improve equine breeding and stud farm outcomes. Vet World 2025 Feb;18(2):311-328.
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