Fertilization rates in superovulated and spontaneously ovulating mares.
Abstract: Embryo recovery per ovulation has been shown to be lower in superovulated mares than in untreated controls. The objectives of this study were to 1) determine whether follicles stimulated with superovulatory treatment ovulate or luteinize without ovulation, 2) determine fertilization rates of oocytes in oviducts of superovulated and control mares, and 3) evaluate viability of early stage embryos from superovulated and control mares when cultured in equine oviductal cell-conditioned medium. Cyclic mares were randomly assigned to 1 of 2 groups (n=14 per group) on the day of ovulation (Day 0): Group 1 received 40 mg of equine pituitary extract (EPE; i.m.) daily beginning on Day 5 after ovulation; mares assigned to Group 2 served as untreated controls. All mares were given 10 mg PGF(2alpha) on Day 5 and Day 6, and 3,300 IU of human chorionic gonadotropin (hCG) were administered intravenously once mares developed 2 follicles >/=35 mm in diameter (Group 1) or 1 follicle >/=35 mm in diameter (Group 2). Mares in estrus were inseminated daily with 1 x 10(9) progressively motile spermatozoa once a >/=35 mm follicle was obtained. Two days after the last ovulation the ovaries and oviducts were removed. Ovaries were examined for ovulatory tracts to confirm ovulation, while the oviducts were trimmed and flushed with Dulbeccos PBS + 10% FCS to recover fertilized oocytes. All fertilized oocytes (embryos) recovered were cultured in vitro for 5 d using TCM-199 conditioned with equine oviductal cells. Ninety-two percent of the CL's from EPE mares resulted from ovulations compared with 94% for mares in the control group (P>0.05). The percentages of ovulations resulting in embryos were 57.1 and 62.5% for EPE-treated and control mares, respectively (P>0.05). Eighty-eight (Group 1) and 91% (Group 2) of the freshly ovulated oocytes recovered were fertilized (P>0.05). After 5 d of culture, 46.4 and 40.0% of the embryos from EPE-treated and control mares developed to the morula or early blastocyst stage (P>0.05). In summary, the CL's formed in superovulated mares were from ovulations not luteinizations. Although embryo recovery was less than expected, fertilization rates and embryo development were similar (P>0.05) between superovulated and control mares.
Publication Date: 1994-01-01 PubMed ID: 16727495DOI: 10.1016/0093-691x(94)90192-lGoogle Scholar: Lookup
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Summary
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This study investigates the fertilization rates and early embryonic viability in hormonally superovulated and naturally ovulating mares. The main findings reveal that despite lower than anticipated embryo recovery, fertilization rates and embryo viability remain consistent in both superovulated and non-treated mares.
Methodology
- The research was conducted on cyclic mares arbitrarily grouped into the ones that received hormonal treatment and untreated ones.
- The treated group was given 40mg of equine pituitary extract (EPE) daily, starting from the fifth day after ovulation to stimulate superovulation, whereas the untreated group acted as control.
- Both groups were also administered other hormones like PGF(2alpha) and human chorionic gonadotropin (hCG) to manage ovulation and trigger it when a follicle of minimum 35mm in diameter was identified in their reproductive system. The number of follicles triggered differed between the two groups (2 for treated and 1 for untreated).
- During estrus, daily insemination occurred with a specific volume of progressively motile spermatozoa once an adequate-sized follicle was detected.
- The ovaries and oviducts of the mares were then surgically removed post two-day ovulation. The ovaries were used to verify ovulation trails while the oviducts served to recover fertilized oocytes.
- The resultant embryos were in vitro cultured for five days in special media.
Results
- The examination of the corpora lutea (CL’s — hormone-secreting structures formed post-ovulation) in the EPE-treated mares showed that 92% resulted from ovulations not luteinizations, making it comparable to the control group (94%).
- The percentage of ovulations leading to embryos was also similar for both EPE-treated mares (57.1%) and control mares (62.5%).
- About 88% of the freshly ovulated oocytes recovered from Group 1 (EPE-treated) and 91% from Group 2 (Untreated) were fertilized, thereby indicating no significant difference between the two.
- A comparison of in vitro cultured embryos from EPE-treated and control mares showed 46.4% and 40.0% development to the morula or early blastocyst stage, respectively. The results were statistically insignificant.
Conclusion
- The overall conclusion drawn from the study was that, despite less than expected embryo recovery, the fertilization rates and early stage embryo development were not significantly different between mares that were hormonally induced to superovulate and those that didn’t receive treatment.
- These findings provide valuable insight for breeders and professionals in animal husbandry looking to optimize breeding protocols in mares.
Cite This Article
APA
Dippert KD, Jasko DJ, Seidel GE, Squires EL.
(1994).
Fertilization rates in superovulated and spontaneously ovulating mares.
Theriogenology, 41(7), 1411-1423.
https://doi.org/10.1016/0093-691x(94)90192-l Publication
Researcher Affiliations
- Animal Reproduction and Biotechnology Laboratory Colorado State University Fort Collins, CO 80523, USA.
Citations
This article has been cited 1 times.- Malmsten J, Dalin AM. Reproductive failure in moose (Alces alces) due to embryonic mortality and unfertilized oocytes. Acta Theriol (Warsz) 2014;59(3):449-455.
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