Effects of medroxyprogesterone acetate (MAP) on ovarian antral follicle development, gonadotrophin secretion and response to ovulation induction with gonadotrophin-releasing hormone (GnRH) in seasonally anoestrous ewes

Bartlewski, Pawel M.; Aravindakshan, Jayaprakash; Beard, A.P.; Nelson, Marita L.; Arteaga, Miguel Batista; Cook, Susan; Rawlings, N. C.

doi:10.1016/j.anireprosci.2003.10.002

Cited by 19 publications

(9 citation statements)

References 31 publications

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“…A delayed (Lopez‐Alonso et al. 2005) or truncated (Bartlewski et al. 2004) preovulatory LH discharge may result in diminished ovulatory responses in ewes.…”

Section: Discussionmentioning

confidence: 99%

Ovarian Responses, Hormonal Profiles and Embryo Yields in Anoestrous Ewes Superovulated with Folltropin®‐V after Pretreatment with Medroxyprogesterone Acetate‐releasing Vaginal Sponges and a Single Dose of Oestradiol‐17β

Bartlewski¹,

Alexander²,

Rawlings³

et al. 2007

Reprod Domestic Animals

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In ruminants, superovulatory treatments started at the time of follicular wave emergence result in greater and less variable ovulatory responses and embryo yields compared with the treatments begun in the presence of a large growing antral follicle(s) from the previous waves. The progesterone-oestradiol treatment is routinely used for follicular wave synchronization in cattle. The main objective of this study was to characterize the ovarian responses, hormonal profiles and in vivo embryo production in anoestrous Rideau Arcott ewes (May-June), which were superovulated after pretreatment with medroxyprogesterone acetate (MAP)-releasing intravaginal sponges and a single dose of oestradiol-17beta (E(2)-17beta). Six days after insertion of MAP sponges, eight ewes were given an i.m. injection of 350 microg of E(2)-17beta (E(2)-17beta-treated ewes); 10 ewes were given an i.m. injection of vehicle (control ewes). Multiple-dose Folltropin-V treatment, followed by the bolus injection of GnRH (50 microg i.m.), began 6 days after E(2)-17beta/vehicle injection. Transrectal ovarian ultrasonography revealed that: (i) the interval between E(2)-17beta/vehicle injection and regression of all follicles > or =5 to 3 mm in diameter was shorter (p < 0.01; 2.6 +/- 0.4 vs 4.8 +/- 0.6 days respectively); and (ii) the interval between injection and emergence of the next follicular wave was longer (p < 0.05; 5.4 +/- 0.3 vs 1.2 +/- 0.4 days, respectively) in E(2)-17beta-treated than in control ewes. During the 6 days after injection, the mean FSH peak concentration and basal FSH concentration were lower (p < 0.01) in E(2)-17beta-treated ewes. The mean ovulation rate and the number of recovered embryos did not differ (p > 0.05) between the two groups of ewes. However, the number of luteinized unovulated follicles per ewe, and the variability in the number of luteal structures and overall embryo yield were less (p < 0.05) in E(2)-17beta-treated compared with control ewes. In conclusion, the MAP-E(2)-17beta pretreatment significantly reduced the variability in ovarian responses and embryo yields, without affecting the embryo production in superovulated anoestrous ewes.

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“…A delayed (Lopez‐Alonso et al. 2005) or truncated (Bartlewski et al. 2004) preovulatory LH discharge may result in diminished ovulatory responses in ewes.…”

Section: Discussionmentioning

confidence: 99%

Ovarian Responses, Hormonal Profiles and Embryo Yields in Anoestrous Ewes Superovulated with Folltropin®‐V after Pretreatment with Medroxyprogesterone Acetate‐releasing Vaginal Sponges and a Single Dose of Oestradiol‐17β

Bartlewski¹,

Alexander²,

Rawlings³

et al. 2007

Reprod Domestic Animals

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“…This was in agreement with the report of Husein et al [20] which showed that ewes ovulated 25 to 30 h after the time of estrus onset. It has been suggested that the diameter of ovarian follicles that result in ovulation is 5.0 mm or more for ewes [21][22][23][24]. Barrett et al [25] has reported that the diameter of follicles at time of ovulation in ewes during the non-breeding season is 6.1 ± 0.1 mm, and that the follicles are smaller compared with those during the breeding season.…”

Section: Discussionmentioning

confidence: 99%

Comparison of Estrus Induction and Subsequent Fertility with Two Different Intravaginal Devices in Ewes during the Non-Breeding Season

Kohno

Okamoto

Iida

et al. 2005

Journal of Reproduction and Development

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Abstract.Two experiments were conducted to compare the effect of estrus induction by controlled internal drug release (CIDR) and intravaginal cream containing 500 mg progesterone (P cream) in ewes during the non-breeding season. In the first experiment, twenty-four ewes were randomly grouped for two treatments with the different intravaginal devices for 12 days: Group A was the CIDR group and Group B was the P cream group. Blood was collected from all treated ewes, and progesterone (P4), estradiol 17-β (E2) and luteinizing hormone (LH) concentrations were measured by enzyme immunoassay. In the second experiment, the conception rates from natural mating, estrusdetected AI (inseminated 12 h after estrus detection), or fixed-time AI (inseminated 42 h after removal of an intravaginal device) in 127 ewes treated with CIDR or P cream were compared. In Experiment 1, the rate of estrus induction and the time of estrus onset after device removal were 91.7% and 36.3 ± 15.7 h in Group A, and 100% and 35.0 ± 12.6 h in Group B, respectively. There were no significant differences between the devices. The mean plasma P4 concentration in Group B was significantly (P<0.01) lower than Group A between day -9 and day -1 (Day 0: the day of device removal). However, no significant differences were found in the mean E2 concentrations of the two groups after treatment. The mean time of estrus onset in ewes with an observed LH surge and the time of LH surge after treatment were 23.3 ± 8.7 h and 30.3 ± 5.0 h for Group A and 27.6 ± 6.5 and 26.3 ± 8.0 h for Group B, respectively, and there were no significant differences. However, a significant difference (P<0.05) was found in the mean time from the time of estrus onset to LH surge between Group A (6.4 ± 6.7 h) and Group B (-1.3 ± 4.1 h). In Experiment 2, the conception rates for natural mating, estrus-detected AI, and fixed-time AI were 55.0, 29.4, and 25.0% for Group A and 40.7, 25.0, and 42.1% for Group B, respectively, and there were no significant differences. These results suggest that the effect of induction of estrus and ovulation and the rate of conception after treatment were comparable to CIDR even though the plasma P4 concentration of the P cream method tended to be low during the insertion period. Key words: Estrus induction, Fertility, Intravaginal device, Non-breeding season, Sheep (J. Reprod. Dev. 51: [805][806][807][808][809][810][811][812] 2005) ethods of estrus induction in ewes using various intravaginal devices impregnated with progesterone or synthetic progestogen have been developed and used throughout the world.The main method is an intravaginal sponge

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“…A number of different mechanisms have been suggested to be responsible for the formation of inadequate luteal phases in sheep, including defective maturation of the preovulatory follicle (Keisler & Keisler 1989, Hunter et al 1986, White et al 1987, Southee et al 1988a, Khalid et al 1997, Lund et al 1999, Bartlewski et al 2001, perhaps due to an inappropriate pattern of LH stimulation of the follicle prior to the LH surge (McLeod et al 1982a, Wright et al 1983, attenuation of the LH surge (Bartlewski et al 2004), inadequate luteinization (Atkinson 1988, Hunter et al 1988, inappropriate luteal support of the new CL (Hunter et al 1988) and/or increased susceptibility to luteolytic stimuli (Hunter et al 1989, Beard & Hunter 1996 arising from the uterus (Southee et al 1988b, Hu et al 1991, though see Rahmanian and Murdoch 1987).…”

Section: Introductionmentioning

confidence: 99%

Corpora lutea induced by gonadotrophin-releasing hormone treatment of anoestrous Welsh Mountain ewes: reduced sensitivity to luteinizing hormone in vivo and to chorionic gonadotrophin in vitro

Bramley

Stirling²,

Menzies³

et al. 2005

Reproduction

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Seasonally anoestrous Welsh Mountain ewes received 250 ng gonadotrophin-releasing hormone (GnRH) every 2 h, with (Group 1;n= 13) or without (Group 2;n= 14) progesterone priming for 48 h. Fourteen control ewes (Group 3) were studied during the luteal phase in the breeding season. Animals in Group 4 (n= 12) received progesterone priming followed by 250 ng GnRH at increasing frequency for 72 h, while ewes in Group 5 (n= 13) were given three bolus injections of 30 μg GnRH at 90-min intervals. All treatment regimens induced ovulation. However, only corpora lutea (CL) from ewes in Group 3 (breeding season) or Group 4 exhibited normal luteal function. Luteal luteinizing hormone (LH) receptor levels were significantly higher on day 12 than day 4, and CL from groups with adequate CL (3 and 4) had significantly higher125I-human chorionic gonadotrophin (hCG)-binding levels than the three groups with inadequate CL on day 12. LH-binding affinity was unchanged. Exogenous ovine LH (10 μg)in vivoon days 3 or 11 after ovulation induced a pulse of progesterone in ewes with adequate CL: however, ewes in Groups 1, 2 and 5 showed no significant response. Basal progesterone secretionin vitrowas significantly greater on day 4 than on day 12. Maximal steroidogenic responses of adequate and inadequate CL to hCG and to dibutyryl cyclic-3′,5′-AMP were similar at both stages of the luteal phase. However, the EC50for hCG on days 4 and 12 was 10-fold lower for groups with an adequate CL (0.1 IU hCG/ml) than for inadequate-CL groups (1 IU hCG/ml;P<0.05). Thus, in addition to the well-characterized premature sensitivity of GnRH-induced inadequate CL to endometrial luteolysin, we have shown (1) a marked decrease in total number of cells in the CL, a profound reduction in vascular surface area, and a decrease in mean large luteal cell volume (with no change in large luteal cell numbers), (2) decreased luteal LH receptor and progesterone content compared with adequate CL and (3) that CL that were becoming, or were destined to become, inadequate failed to respond to ovine LHin vivoand were 10-fold less sensitive to hCG in terms of luteal progesterone secretionin vitro.

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Effects of medroxyprogesterone acetate (MAP) on ovarian antral follicle development, gonadotrophin secretion and response to ovulation induction with gonadotrophin-releasing hormone (GnRH) in seasonally anoestrous ewes

Cited by 19 publications

References 31 publications

Ovarian Responses, Hormonal Profiles and Embryo Yields in Anoestrous Ewes Superovulated with Folltropin®‐V after Pretreatment with Medroxyprogesterone Acetate‐releasing Vaginal Sponges and a Single Dose of Oestradiol‐17β

Ovarian Responses, Hormonal Profiles and Embryo Yields in Anoestrous Ewes Superovulated with Folltropin®‐V after Pretreatment with Medroxyprogesterone Acetate‐releasing Vaginal Sponges and a Single Dose of Oestradiol‐17β

Comparison of Estrus Induction and Subsequent Fertility with Two Different Intravaginal Devices in Ewes during the Non-Breeding Season

Corpora lutea induced by gonadotrophin-releasing hormone treatment of anoestrous Welsh Mountain ewes: reduced sensitivity to luteinizing hormone in vivo and to chorionic gonadotrophin in vitro

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