Follicular and FSH responses to parturition during the anovulatory season in mares.
Abstract: The ovaries of periparturient pony mares (n=9 to 16 parturitions per month for January to April) were scanned ultrasonically on the day of parturition, while those of postpartum and control mares (n=12) were examined at least twice weekly. Four mares had apparent lactational anovulation (incidence, 7%) that corrected spontaneously (1 mare) or within 14 d after the weaning of foals on August 10 (3 mares). All but 2 of the postpartum ovulations occurred after April 29; that is, parturition did not effectively stimulate ovulation in ponies foaling during the anovulatory season. Mean diameter of the largest follicle per month increased (P<0.001) progressively in the controls (means: 11.4, 14.4, 19.0 and 24.5 mm for January to April, respectively). In the parturient mares, the diameter of the largest follicle on day of parturition did not increase over months (range of means: 13.6 to 16.9 mm), indicating that a suppressive effect of pregnancy counteracted the stimulatory effect of season. Within each month of parturition, diameter of the largest follicle increased (P<0.05) between Day 0 (day of parturition) and Day 3 or 7. Blood samples for FSH assay were taken daily for 14 d from 6 mares with parturition in the middle of each month and from 6 controls on the corresponding calendar days. In periparturient mares, a significant increase in mean FSH concentrations occurred for all months of parturition between Day-2 and Day 0, followed by a significant decrease between Day 3 and Day 7. Maximum means for the periparturient FSH profile were temporally related to the beginning of follicular growth. In the controls, FSH concentrations were not affected by month or day, or by their interaction. Within each month, mean FSH concentrations were lower (P<0.05) in the periparturient mares than in the controls (averaged over all months: 3.9+/-0.1 versus 7.9+/-0.3 ng/ml) even though follicular growth was greater following parturition than during the corresponding calendar days in controls.
Publication Date: 1994-02-02 PubMed ID: 16727417DOI: 10.1016/0093-691x(94)90172-fGoogle Scholar: Lookup
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Summary
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The research investigates the impact of parturition (childbirth) on the ovulatory processes in ponies, particularly during the anovulatory season. The study practices ultrasonic scanning pre and post childbirth on several female ponies, measuring associated hormonal changes and follicular sizes to deduce effects.
Study Methodology
- The team used advanced ultrasonic technology to scan the ovaries of pony mares during parturition and post-birth. Over a four-month period (from January to April), up to 16 parturitions were scanned.
- In addition to parturition, control mares were studied twice weekly, offering a benchmark for statistical comparisons.
- Blood samples were collected daily from 6 mares undergoing parturition in the middle of each month and 6 controls on the equivalent calendar days. These samples helped assess fluctuations in FSH levels, a hormone that stimulates follicular growth.
Key Observations
- Four mares showed signs of lactational anovulation, a temporary absence of ovulation which resolved either naturally or shortly after weaning.
- All but two of the observed ovulations took place after April-end, indicating that parturition might not effectively trigger ovulation in mares foaling during the anovulatory season.
- The researchers noted an increased diameter of the largest follicle each month in the control mares, whereas a counteractive effect was observed in birthing mares due to the suppressive influence of pregnancy.
- In birthing mares, a significant increase in FSH level was noted from pre-delivery to the day of delivery, followed by a drop in levels from Day 3 to Day 7 post-delivery. These FSH peaks coincided with the start of follicular growth.
Findings and Conclusion
- Despite having lower average FSH levels compared to the controls, birthing mares exhibited more significant follicular growth post-delivery than the average growth during corresponding calendar days in control mares.
- These findings suggest the complex interplay between birthing, FSH levels, and follicle growth might be affected by seasonality and the physiological stress of childbirth, providing useful insights into fertility cycles and reproduction in equine species.
Cite This Article
APA
Ginther OJ, Baucus KL, Bergfelt DR.
(1994).
Follicular and FSH responses to parturition during the anovulatory season in mares.
Theriogenology, 41(3), 613-627.
https://doi.org/10.1016/0093-691x(94)90172-f Publication
Researcher Affiliations
- Animal Health and Biomedical Sciences, 1655 Linden Drive, University of Wisconsin-Madison, Madison, WI 53706, USA.
Citations
This article has been cited 1 times.- Cardona-García M, Jiménez-Escobar C, Ferrer MS, Maldonado-Estrada JG. Follicular Dynamics and Pregnancy Rates during Foal Heat in Colombian Paso Fino Mares Bred under Permanent Grazing. Animals (Basel) 2024 Feb 29;14(5).
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