Control of ovarian follicles activity in the ewe

Bister, Jean‐Loup; Noël, B; Perrad, B; Mandiki, Syaghalirwa N.M.; Mbayahaga, J.; Paquay, R.

doi:10.1016/s0739-7240(99)00047-8

Cited by 55 publications

(34 citation statements)

References 5 publications

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“…No differences were observed in the first wave of follicular growth and the ovulatory follicular wave at the beginning of breeding season. These results (Table 1 and 2) are similar to those obtained in previous studies in which the number of small (2 to 3.5 mm), medium (4 to 5 mm) and large (greater than 5 mm) follicles were compared at the beginning, middle and end of the breeding season (Bister et al, 1999). These authors concluded that the number of small, medium and large follicles did not differ across the periods of time.…”

Section: Group Variablesupporting

confidence: 89%

“…In all groups, control and experimental, the maximum diameter of the ovulatory follicles was similar to those described by Ravindra et al (1994), Leyva et al (1998), Bister et al (1999) and Gonzalez de Bulnes et al (2001) (Table 2). In previous studies, Barrett et al (2004) reported that ovulatory follicles were smaller during the anestrous season (6.1±0.1 mm) than those observed during the breeding season (7.5±0.5 mm).…”

Section: Group Variablesupporting

confidence: 82%

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Ovarian response of Suffolk ewes to estrous synchronization using short-term protocol

et al. 2012

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-The efficacy of estrus synchronization using short-term protocol was evaluated by ultrasound exams in Suffolk ewes during the pre-breeding season. The control Group (n = 12) was synchronized by treatment for 12 days with vaginal sponges impregnated with medroxyprogesterone acetate, and 400 IU eCG at sponge withdrawal. Experimental groups I, II and III kept the sponge in place for 4 days, and 100 μg of PGF 2α was administered at sponge withdrawal. Additionally, Group I (n = 12) had 0.1 mg of estradiol benzoate (EB) administered during sponge placement and 50 μg of GnRH 48 hours after sponge removal. Group II (n = 6) had 35 mg of progesterone (P4) injected, and 0.1 mg of EB administered during sponge placement, 400 IU eCG at withdrawal and 48 hours after, 50 μg GnRH were administrated.Group III (n = 12) had 35 mg of P4 and 0.2 mg of EB administered at sponge placement, 400 IU eCG at withdrawal, and 50 μg of GnRH was administrated after 56 hours. Ovaries were monitored through ultrasound scanning. Concerning the first wave, no difference was detected between the control group and the experimental groups. However, the characteristics of ovulatory wave were significantly different between the groups. The duration of the follicular wave was shorter for Group III than for Group II. The follicle in Group I reached its maximum diameter before the Group II. The diameter of the follicle at the sponge withdrawal in the control group was larger than in Group I. After sponge withdrawal, the follicular growth rate was smaller in the control group than in Group III. The maximum diameter of the follicle in Group II was larger than in the other groups. The short-term protocol in which estrogen was used did not synchronize the emergence of the wave of follicular development.

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Section: Group Variablesupporting

confidence: 89%

Section: Group Variablesupporting

confidence: 82%

Ovarian response of Suffolk ewes to estrous synchronization using short-term protocol

et al. 2012

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“…Several authors have reported an increased ovulation rate after treatment with melatonin implants in both seasonal (Robinson et al, 1991;Haresign, 1992) and Mediterranean ewes (Forcada et al, 1995;Zuniga et al, 2002). Some studies using synchronized ewes have found that a medium-term treatment with melatonin does not improve ovulation rate by modifying the timing of follicle emergence, but increasing the number of ovulatory follicles by decreasing the atresia of medium and large follicles Noel et al, 1999). However, melatonin treatments do not induce significant increases in ovulation rate following a superovulatory treatment, either in anoestrus or during the breeding season (McEvoy et al, 1998), suggesting that a protocol of several FSH injections probably recruits all the follicles independently of atresia mechanisms (McEvoy et al, 1998).…”

Section: Effect Of Melatonin On the Ovine Ovarymentioning

confidence: 99%

Effect of exogenous melatonin on the ovary, the embryo and the establishment of pregnancy in sheep

Abecia¹,

Forcada²,

Casao³

et al. 2008

Animal

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Administration of melatonin to advance the breeding season in sheep has been widely used, since this hormone conveys the photoperiodic signal to the reproductive neuroendocrine axis. An increased lambing percentage has been reported following such treatment during anoestrus, which could be mediated through a higher rate of embryonic survival, either by an improvement in luteal function or by a reduction in the antiluteolytic mechanisms. The aim of this article is to review the body of knowledge on the effect of melatonin on the ovine ovary, the embryo and the establishment of pregnancy. Some studies using synchronized ewes have found that melatonin treatments during anoestrus do not improve ovulation rate by modifying the timing of follicle emergence, but increasing the number of ovulatory follicles by decreasing the atresia of medium and large follicles. On the other hand, the addition of melatonin to the in vitro maturation medium does not improve oocyte maturation rate in oocytes from sheep ovaries recovered either in anoestrus or in the breeding season. However, a luteotrophic effect of melatonin at either short or medium term has been reported. We have recently observed that melatonin implants tend to improve the survival of embryos collected from ewes after superovulation in anoestrus. More specifically, melatonin induced a significant reduction of the number and rate of non-viable (degenerate and retarded) embryos. Preliminary data from our laboratory suggest that the uterine sensitivity to progesterone -in terms of progesterone receptor expression -of superovulated ewes could be reduced by melatonin treatment. It can be concluded that the success of exogenous melatonin as a means to improve lamb production of sheep is due, at least in part, to an improvement of luteal support and embryonic survival.

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“…There was a report that the small follicles of the ewes carrying the Booloora fecundity gene have higher estrogen producting ability [23], and Dorset cross-breed ewes with th e Boolo ora F gene had few er undergrowth CL, as they had immature follicles. Therefore, it was considered that Doset-crossed ewes had a low percentage of abnormal CL.…”

Section: Hypoplasiamentioning

confidence: 99%

Incidence of Abnormal Corpus Luteum in Superovulated Ewes

Okada

Kamada

Jeon

et al. 2000

Journal of Reproduction and Development

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Abstract. In the present study, in order to investigate the incidence time of abnormal corpus luteum (CL) in superovulated ewes, CL formation was observed and plasma progesterone (P4) and estradiol-17β(E2) profiles were investigated during the non-breeding and breeding seasons in three breeds of ewes. The ewes were treated with a fluorogesterone acetate (FGA) sponge for 12 days, and a single injection of 20 mg pFSH on Day -2 and 500 IU eCG on Day -1 (FGA sponge removal: Day 0), for estrous synchronization and superovulation. All ewes were given an injection of 100 µg gonadotropin releasing hormone analogue (GnRH analogue) at estrous detection and inseminated with frozenthawed semen by laparoscope on a fixed-time basis (32-36 h after FGA sponge removal). On Day 6.5, the ewes were laparotomized for ovarian response and embryo recovery. Blood was taken from all ewes on Days 0 to 6.5, and the plasma P4 and E2 concentrations were measured by emzyme immunoassay (EIA). According to the ovarian responses on Day 6.5, the ewes were divided into Group N (only normal CL; n=21), Group A (only abnormal CL; n=7) and Group M (both normal and abnormal CL; n=3). The mean P4 profile in Group N continued to rise during the period of blood sampling, and was significantly higher than in Group A which remained under 1 ng/ml and decreased after Days 4 to 4.5. The means E2 levels tended to be higher in Group A than in Group N. In the autumn study, the ewes with abnormal CL on Day 6.5 had already lacked in color on Day 4.5, and the number of large follicles was significantly lower in the ewes with abnormal CL than in those with only normal CL. These results indicate that the phenomenon of abnormal CL formation at 3-3.5 days after estrus is not due to premature luteal regression of functionally complete CL, but to luteal hypoplasia of incomplete CL with a short lifespan, but the cause of abnormal CL was not determined in the study.

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Control of ovarian follicles activity in the ewe

Cited by 55 publications

References 5 publications

Ovarian response of Suffolk ewes to estrous synchronization using short-term protocol

Ovarian response of Suffolk ewes to estrous synchronization using short-term protocol

Effect of exogenous melatonin on the ovary, the embryo and the establishment of pregnancy in sheep

Incidence of Abnormal Corpus Luteum in Superovulated Ewes

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