Reproductive performance of donor mares subsequent to eFSH treatment in early vernal transition: Comparison between the first, second, and mid-season estrous cycles of the breeding season.
Abstract: The objective was to compare the reproductive performances associated with the first (Cycle-1), second (Cycle-2), and mid-season (MS-Cycle) ovulations of the breeding season in donor mares that were treated with equine-FSH (eFSH) in the early vernal transition. Mares (n=15) kept under ambient light were examined ultrasonographically per-rectum starting January 30. When an ovarian follicle > or =25mm in diameter was detected, twice daily eFSH treatments were initiated. The eFSH treatments ceased when a follicle > or =35mm was detected, and 36h later hCG was administered. Thereafter, mares were artificially inseminated every 48h until ovulation (Day 0). Trans-cervical embryo recovery attempts were performed on Day 8, and subsequently PGF2alpha was administered. Equine FSH was not administered in the subsequent estrous cycles. In Cycle-2 and in the MS-Cycle, hCG was administered when a follicle > or =35mm was detected; breeding, embryo recovery, and PGF2alpha administration, were similar to Cycle-1. Mares had an untreated estrous cycle (no treatment or breeding) between Cycle-2 and the MS-Cycle. All mares developed follicle(s) > or =35mm after 4.9+/-0.6 days of eFSH treatment, and subsequently ovulations occurred; mean (95% CI) interval from treatment initiation to ovulation was 7.9 (6.5-9.3) days. The number of preovulatory follicles (> or =30mm) at the time of hCG administration (Cycle-1: 2.2+/-0.3 compared with Cycle-2: 1.0+/-0 compared with MS-Cycle: 1.1+/-0.1 follicles), and the number of ovulations (2.5+/-0.4 compared with 1.0+/-0 compared with 1.1+/-0.1 ovulations) were greater (p<0.05) in Cycle-1. Nevertheless, mean embryo numbers did not differ among cycles (0.8+/-0.2 compared with 0.5+/-0.1 compared with 0.5+/-0.1 embryo/mare). On average, embryo morphology grade was less (p<0.05) in Cycle-1 as compared to non-eFSH cycles (combined Cycle-2 and MS-Cycle). This impaired embryo quality could be due to a seasonal effect, or negative effect of the eFSH treatment, which was possibly related to alterations in the hormonal environment (estradiol-17beta and progesterone). A prolonged IOI (>21 days) was recorded in 7 of 15 mares following the Cycle-1 ovulation, but not subsequently. In conclusion, eFSH treatment of vernal transitional donor mares stimulated ovulation within only few days of treatment, and the following embryo recovery rate was at least as good as in the subsequent estrous cycles; however, on average, embryos were morphologically impaired. In subsequent estrous cycles in the breeding season, ovulations, embryo recovery rates, and embryo variables did not appear to be negatively affected; however, the first inter-ovulatory interval of the breeding season was prolonged in approximately half of the mares.
Publication Date: 2008-12-24 PubMed ID: 19171444DOI: 10.1016/j.anireprosci.2008.12.008Google Scholar: Lookup
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- Journal Article
- Research Support
- Non-U.S. Gov't
Summary
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This research investigates the effects of equine-FSH (eFSH) treatment on the reproductive performance of donor mares during early vernal transition, studying the diverse ovulation patterns of the first, second, and mid-season cycles of the breeding season and the quality of resulting embryos.
Research Methodology
- 15 mares were tested from January 30, with daily ultrasonographic examinations to track the development of ovarian follicles.
- When a follicle reached 25mm or larger, twice daily eFSH treatments were initiated to stimulate follicular growth.
- These treatments were stopped when a follicle of 35mm or larger was detected, whereafter the horses were administered hCG, a hormone that triggers ovulation, 36 hours later.
- The mares were artificially inseminated every two days until they ovulated (Day 0), and attempts to recover embryos were made on Day 8.
- In Cycle-2 and the MS-Cycle, the hCG administration procedure was repeated, although without the eFSH treatments. An untreated estrous cycle intervened between Cycle-2 and the MS-Cycle.
Research Findings
- All mares developed follicles of 35mm or larger after roughly 5 days of eFSH treatment, and all of them ovulated; the average time from the start of treatment to ovulation was around 8 days.
- The number of preovulatory follicles and resulting ovulations were higher in Cycle-1. Yet the number of recovered embryos did not statistically differ among the cycles.
- On average, the morphology of the embryos derived from Cycle-1 was poorer compared to those from the untreated cycles. This outcome could be attributed to a seasonal effect or potentially negative side effects of eFSH treatment.
- A prolonged IOI (inter-ovulatory interval) of more than 21 days was noted in nearly half of the mares following Cycle-1 ovulation, implying potential disruption to the mares’ reproductive cycles.
Research Conclusion
- eFSH treatment stimulated ovulation in the majority of the donor mares within only a few days of treatment commencement, and successful embryo recovery was achieved in subsequent estrous cycles.
- On average, the embryos from eFSH-treated cycles were morphologically compromised, suggesting potential detriment linked to eFSH treatment or seasonal influences.
- In spite of pronounced follicular development and ovulation, the first inter-ovulatory interval of the breeding season was typically extended in mares post the first cycle of treatment. The potential long-term effect of this delay warrants further research.
Cite This Article
APA
Raz T, Hunter B, Carley S, Card C.
(2008).
Reproductive performance of donor mares subsequent to eFSH treatment in early vernal transition: Comparison between the first, second, and mid-season estrous cycles of the breeding season.
Anim Reprod Sci, 116(1-2), 107-118.
https://doi.org/10.1016/j.anireprosci.2008.12.008 Publication
Researcher Affiliations
- Department of Large Animal Clinical Sciences, University of Saskatchewan, Saskatoon, Canada. tal.raz@usask.ca
MeSH Terms
- Animals
- Breeding
- Chorionic Gonadotropin / pharmacology
- Embryonic Development / drug effects
- Embryonic Development / physiology
- Estradiol / blood
- Estrus / drug effects
- Estrus / physiology
- Female
- Follicle Stimulating Hormone / pharmacology
- Horses / physiology
- Ovulation / drug effects
- Ovulation / physiology
- Ovulation Induction
- Pregnancy
- Progesterone / blood
- Reproduction / drug effects
- Reproduction / physiology
- Seasons
- Superovulation / drug effects
- Superovulation / physiology
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