Factors affecting pre-ovulatory follicle diameter in the mare: the effect of mare age, season and presence of other ovulatory follicles (multiple ovulation).
Abstract: The importance of elucidating factors affecting reproductive performance and efficiency is of paramount concern to the equine industry. Oocyte viability is known to be one of the determinants of reproductive success and evidence suggests that it may be linked to follicle size. The aims of this study were, therefore, to ascertain: i) the average diameter and range of pre-ovulatory follicles in Thoroughbred mares; ii) whether this is affected by either mare age, time within the breeding season, or the presence of multiple pre-ovulatory follicles (MO). One thousand, four hundred and ninety two Thoroughbred mares, aged 2-26 years, were examined with ultrasound to ascertain ovulation date to within 24h, and pre-ovulatory follicle(s) (F1) diameter. Mares were divided into groups according to age (7 groups, 2-4 yr, 5-7 yr, 8-10 yr, 11-13 yr, 14-16 yr, 17-19 yr, >19 yr), time within the season (16 half-month groups, from Feb 1(st) to Sept 30(th)), and pre-ovulatory follicles (single, {SO} or multiple {MO}). Overall average F1 diameter was 39.95 ± 4.84 mm (range 22-50 mm). Mare age had a significant (P 19 yrs) as did season (largest F1 44.20 ± 3.95 mm, Feb 1(st)-14(th); smallest F1 33.74 ± 4.87 mm, Aug 15(th)-31(st)) and the presence of more than one pre-ovulatory follicle (MO F1 35.45 ± 4.53 mm; SO F1 37.44 ± 4.84 mm). In conclusion older mares, bred towards the end of the breeding season, especially if MO were present, were more likely to ovulate from smaller follicles. If, as suggested, small pre-ovulatory follicle size is associated with low oocyte viability, then this may account, at least in part, for the poor fertility rates characteristic of older MO mares, bred later in the season and so justify increased monitoring and careful reproductive management of such mares.
Copyright © 2010 Elsevier Inc. All rights reserved.
Publication Date: 2010-07-07 PubMed ID: 20615543DOI: 10.1016/j.theriogenology.2010.05.027Google Scholar: Lookup
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Summary
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The study investigates factors that influence the diameter of pre-ovulatory follicles in thoroughbred mares. It specifically looks at the impact of the mare’s age, time of the year within the breeding season, and the presence of multiple ovulatory follicles.
Objective of the Study
- The study aims to understand and establish the average diameter and variety of pre-ovulatory follicles in thoroughbred mares.
- The research seeks to examine if the mare’s age, the time within the breeding season, or the presence of multiple pre-ovulatory follicles affects the pre-ovulatory follicle’s size.
- The underlying goal is to link factors affecting the mare’s reproductive performance, especially oocyte viability, which is widely acknowledged as a determinant of reproductive success.
Methodology
- The researchers studied over one thousand thoroughbred mares ranging in age from 2 to 26 years, using ultrasound to determine ovulation data and pre-ovulatory follicles diameter within a 24-hour timeframe.
- The mares were subsequently grouped according to their respective ages, breeding season times, and the presence of either single or multiple pre-ovulatory follicles.
Findings
- Researchers discovered an overall average pre-ovulatory follicle diameter of around 39.95 ± 4.84 mm, with the largest follicle being 38.95 ± 5.61 mm in 2-4-year-old mares, and the smallest follicle being 33.30 ± 4.66 mm in mares older than 20 years.
- Significant variations were found based on the mare’s age, breeding season timing, and presence of multiple pre-ovulatory follicles, with older mares tending to ovulate from smaller follicles, especially towards the end of the breeding season and when multiple ovulatory follicles were detected.
Conclusion and Implications
- The study concludes that smaller pre-ovulatory follicle size, likely correlated with low oocyte viability, might contribute to poor fertility rates, especially in older mares bred late in the season and with multiple ovulatory follicles present.
- These findings could lead to enhanced monitoring and reproductive management strategies for such mares to improve their fertility rates.
Cite This Article
APA
Morel MC, Newcombe JR, Hayward K.
(2010).
Factors affecting pre-ovulatory follicle diameter in the mare: the effect of mare age, season and presence of other ovulatory follicles (multiple ovulation).
Theriogenology, 74(7), 1241-1247.
https://doi.org/10.1016/j.theriogenology.2010.05.027 Publication
Researcher Affiliations
- Institute of Biological, Environmental and Rural Sciences, Aberystwyth University, Ceredigion, SY23 3AL, UK. mid@aber.ac.uk
MeSH Terms
- Aging / physiology
- Animals
- Female
- Horses / physiology
- Ovarian Follicle / physiology
- Ovulation / physiology
- Seasons
Citations
This article has been cited 5 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.
- Ribeiro MO, Bittencourt RF, Feliciano MAR, Santana ALA, Silva MAA, Felix MD, Santana LR, Barbosa LP. Subdose of human chorionic gonadotropin applied at the Hou Hai acupoint on follicular dynamics and luteal development in donkeys. Anim Reprod 2020 Nov 25;17(4):e20200554.
- Carluccio A, Bucci R, Fusi J, Robbe D, Veronesi MC. Effect of age and of reproductive status on reproductive indices in horse mares carrying mule pregnancies. Heliyon 2020 Oct;6(10):e05175.
- Golestanpour H, Javadi G, Sheikhha MH. Association of GRIA1 polymorphisms with ovarian response to human menopausal gonadotropin in Iranian women. Clin Exp Reprod Med 2020 Sep;47(3):207-212.
- Duguma A, Lemma A, Hibste A. Effect of breed and other animal-related factors on conception rate to artificial insemination with frozen semen in mares in Ethiopia. Trop Anim Health Prod 2019 Jun;51(5):1173-1178.
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