Follicular and gonadotrophic changes during transition from ovulatory to anovulatory seasons.
Abstract: Observations of follicular and gonadotrophic changes were conducted on 14 Pony mares for 31-day periods beginning at the penultimate (second last) ovulation and at the last ovulation of the season. There were no main effects or interaction of day or period on the numbers of small follicles (less than 20 mm). Concentrations of FSH, numbers of large follicles (greater than 20 mm), and oestrous behaviour each showed an effect of day (P less than 0.01), but no effect of period. Concentrations of LH and diameter of the largest follicle each showed an interaction (P less than 0.01) between day and period attributable primarily to smaller values on Days 18--24 after the last ovulation than after the penultimate ovulation. It was concluded that, of the factors considered, failure of ovulation at the onset of the anovulatory season was due to lack of an adequate ovulatory LH surge and final growth of a preovulatory follicle.
Publication Date: 1979-01-01 PubMed ID: 289845
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- Journal Article
- Research Support
- U.S. Gov't
- P.H.S.
Summary
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This research studied the changes in hormone levels and follicular development in ponies at the transition from ovulatory to anovulatory seasons, concluding that the end of the breeding season is marked by insufficient production of Luteinising Hormone (LH) and hindered development of a pre-ovulatory follicle, ultimately preventing ovulation.
Details of the Research
- The study involved a sample of 14 Pony mares, which were observed over two distinct 31-day periods. These periods began at the second-last ovulation and the last ovulation of the breeding season, respectively.
- The research specifically looked at follicles, small and large (less than and greater than 20mm respectively), and the hormones FSH (Follicle Stimulating Hormone) and LH (Luteinising Hormone), which play critical roles in ovulation.
Findings of the Study
- There were no significant changes observed in the number of small follicles across the days of the periods under study.
- Differently, FSH concentration, the number of large follicles, and observable oestrous behaviour all showed significant fluctuation depending on the day. However, these factors did not seem to be influenced by whether mares were in the last or penultimate ovulatory period.
- The study found interactive results with levels of LH and the diameter of the largest follicle. There was a noticeable decrease in these values on days 18 to 24 after the last ovulation when compared to the same timespan after the second last ovulation of the season.
Conclusion of the Research
- Ultimately, the research concluded that the transition to the anovulatory period is largely marked by a failure in the natural ovulation process due to two primary factors: the lack of an adequate ovulatory surge of LH and insufficient growth of a preovulatory follicle.
- This conclusion suggests that changes in these two critical components could be responsible for the inability of the mares to ovulate at the onset of the non-breeding (anovulatory) season.
Cite This Article
APA
Snyder DA, Turner DD, Miller KF, Garcia MC, Ginther OJ.
(1979).
Follicular and gonadotrophic changes during transition from ovulatory to anovulatory seasons.
J Reprod Fertil Suppl(27), 95-101.
Publication
Researcher Affiliations
MeSH Terms
- Animals
- Estrus
- Female
- Gonadotropins, Pituitary / blood
- Horses / physiology
- Light
- Ovarian Follicle / physiology
- Ovulation
- Periodicity
- Pregnancy
- Seasons
Citations
This article has been cited 3 times.- Koskinen E, Huhtinen M, Katila T. Serum progesterone levels in mares in winter and during transitional periods. Acta Vet Scand 1996;37(4):409-14.
- Jongbloet PH, Mulder A, Hamers AJ. Seasonality of pre-ovulatory non-disjunction and the aetiology of Down syndrome. A European collaborative study. Hum Genet 1982;62(2):134-8.
- Jongbloet PH, Vrieze OJ. Down syndrome: increased frequency of maternal meiosis I nondisjunction during the transitional stages of the ovulatory seasons. Hum Genet 1985;71(3):241-8.
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