Evidence of intraovarian follicular dominance effects during controlled ovarian stimulation in a sheep model

González-Bulnes, Antonio; Veiga-López, Almudena

doi:10.1016/j.fertnstert.2007.05.037

Cited by 10 publications

(7 citation statements)

References 45 publications

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“…The ovulatory response and total number of transferable embryos after superovulation are strongly affected by the size and number of antral follicles present in the ovary at the outset of the superovulatory treatment [3,5,6]. Differences in follicular wave status at the beginning of exogenous FSH administration appear to be one of the major contributors to the variability in superovulatory responses in sheep [3,5,6,8,22,23]. Several authors postulated that large ovarian follicles exerted a dominant effect in sheep by reducing FSH availability via estradiol and inhibin A secretion, thereby suppressing the growth of smaller, gonadotropin-dependent antral follicles [5,[22][23][24][25].…”

Section: Introductionmentioning

confidence: 99%

“…Differences in follicular wave status at the beginning of exogenous FSH administration appear to be one of the major contributors to the variability in superovulatory responses in sheep [3,5,6,8,22,23]. Several authors postulated that large ovarian follicles exerted a dominant effect in sheep by reducing FSH availability via estradiol and inhibin A secretion, thereby suppressing the growth of smaller, gonadotropin-dependent antral follicles [5,[22][23][24][25]. Studies have shown a decrease in the number of ovulations in ewes when superovulation was begun in the presence of ovulatory-sized ovarian follicles [3,5,22,23].…”

Section: Introductionmentioning

confidence: 99%

“…Several authors postulated that large ovarian follicles exerted a dominant effect in sheep by reducing FSH availability via estradiol and inhibin A secretion, thereby suppressing the growth of smaller, gonadotropin-dependent antral follicles [5,[22][23][24][25]. Studies have shown a decrease in the number of ovulations in ewes when superovulation was begun in the presence of ovulatory-sized ovarian follicles [3,5,22,23]. A potential codominant effect of the two largest antral follicles (F1 and F2) has also been suggested as the physiological status of F1 and F2 at the outset of the superovulatory regimen in cyclic ewes has been shown to affect the ovulation rate and embryo recovery [25].…”

Section: Introductionmentioning

confidence: 99%

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Comparison of the effects of pretreatment with Veramix sponge (medroxyprogesterone acetate) or CIDR (natural progesterone) in combination with an injection of estradiol-17β on ovarian activity, endocrine profiles, and embryo yields in cyclic ewes superovulated in the multiple-dose Folltropin-V (porcine FSH) regimen

et al. 2015

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Follicular wave status at the beginning of exogenous FSH administration is an important contributor to variability in superovulatory responses in ruminants. Studies in ewes have shown a decrease in the number of ovulations when superovulation is initiated in the presence of ostensibly ovulatory-sized ovarian follicles. Hormonal ablation of large antral follicles with the progestin-estradiol (E2-17β) treatment significantly reduces this variability in superovulated anestrous ewes, but the effects of the treatment in cycling ewes have not yet been assessed. Sixteen Rideau Arcott × Polled Dorset ewes (November-December) received either medroxyprogesterone acetate (MAP)-releasing intravaginal sponges (60 mg) or controlled internal drug release (CIDR) devices (containing 300 mg of natural progesterone) for 14 days (Days 0-14), with a single intramuscular injection of 350 μg of E2-17β on Day 6. The superovulatory treatment consisted of six injections of porcine FSH (Folltropin-V) given twice daily, followed by a bolus GnRH injection (50 μg intramuscular) on Day 15. There were no differences (P < 0.05) in the ovulatory responses and embryo yields between the two groups of ewes. In both subsets of animals, the next follicular wave emerged ∼2.5 days after an E2-17β injection (P > 0.05). A decline in maximum follicle size after an E2-17β injection was more abrupt in CIDR- compared with MAP-treated animals, and the ewes pretreated with exogenous progesterone had significantly more 3-mm follicles at the start of the superovulatory treatment. The metabolic clearance rate of exogenous E2-17β appeared to be greater in MAP-treated ewes, but circulating concentrations of porcine FSH failed to increase significantly after each Folltropin-V injection in CIDR-treated animals. The CIDR-treated ewes exceeded (P < 0.05) their MAP-treated counterparts in serum E2-17β concentrations during superovulation. In spite of differences in antral follicle numbers and endocrine profiles between MAP- and CIDR-treated cyclic ewes receiving E2-17β before ovarian superstimulation, there were no differences in superovulatory responses.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Comparison of the effects of pretreatment with Veramix sponge (medroxyprogesterone acetate) or CIDR (natural progesterone) in combination with an injection of estradiol-17β on ovarian activity, endocrine profiles, and embryo yields in cyclic ewes superovulated in the multiple-dose Folltropin-V (porcine FSH) regimen

et al. 2015

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“…Ovarian ultrasound in sheep has demonstrated that a follicular wave emerges approximately every five days (8) and the corpus luteum is already sensitive to PGF2α at three days after ovulation (19) , whereas follicular dominance presents varied growth patterns. Follicles larger than 5 mm have growth patterns in waves, that is, they appear less dispersed and more concentrated during the estrous cycle (10) .…”

Section: Introductionmentioning

confidence: 99%

Follicular dynamics in dairy sheep within and out of the breeding season employing high or low progesterone concentration in estrous cycle synchronization

Brogni,

Mezzalira

2024

Ciênc. anim. bras.

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Follicular dynamics in dairy sheep is poorly understood. This study assessed the follicular dynamics of dairy sheep within and out of the breeding season by observing the effect of two progesterone concentrations (60 and 120 mg) used in vaginal pessaries in pre-synchronization. The experiment was conducted in April/May and October/November using 40 healthy multiparous dairy ewes predominantly of the Lacaune breed, which underwent daily transrectal ultrasound examinations. The number of ovulations (1.35 vs 1.05), ovulatory follicle diameter (mm) (5.97 vs 5.05), length of the luteal phase (11 vs 9.14 days), and length of the estrous cycle (16.83 vs 16.6 days) were assessed within and out of the breeding season, respectively. The sheep out of the breeding season did not present a corpus luteum at the time of insertion of the vaginal pessary, characterizing anestrus. The ovulatory follicle had a larger diameter in the breeding season even with the shorter length of the follicular phase, suggesting higher viability and quality of the ovulated oocyte. The application of exogenous progesterone extends the luteal phase in the breeding season (11 vs 9.14 days). The anestrus observed out of season suggests the need for a higher progesterone concentration in reproductive protocols. Therefore, breeding protocols can be adapted for different seasons, suggesting the use of vaginal pessaries with a higher progesterone concentration (120 mg) out of the breeding season. The data allowed the characterization of follicular dynamics in dairy sheep, demonstrating their differences in each season based on the use of different progesterone doses in pre-synchronization.

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“…The study of their effects in human beings is impeded for both technical and ethical reasons. Domestic animals may be an alternative; sheep are considered a good experimental model for evaluation of human reproductive endocrinology and ovarian biology (10)(11)(12)(13)(14)(15)(16). Moreover, evaluation of progestogens is also of interest for application in veterinary practice.…”

mentioning

confidence: 99%