Ovarian antral follicular dynamics in sheep revisited: Comparison among estrous cycles with three or four follicular waves

Department of Veterinary Biomedical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, SK, Canada.
Theriogenology (Impact Factor: 1.8). 03/2010; 73(5):670-80. DOI: 10.1016/j.theriogenology.2009.11.007
Source: PubMed


In this study, the characteristics of ovarian follicular waves and patterns of serum concentrations of follicle-stimulating hormone (FSH), estradiol, and progesterone were compared between cycles with three (n=9) or four (n=10) follicular waves in Western White Face (WWF) ewes (Ovis aries). Transrectal ultrasonography and blood sampling were performed daily during one cycle. Estrous cycles were 17.11+/-0.3 and 17.20+/-0.2 d long in cycles with three and four waves, respectively (P>0.05). The first interwave interval and the interval from the emergence of the final wave to the day of ovulation were longer in cycles with three waves compared with those in cycles with four waves (P<0.05). The growth phase (5.1+/-0.5 vs. 3.1+/-0.4 d) and life span (5.67+/-0.3 vs. 4.3+/-0.3 d) of the largest follicle growing in the last or ovulatory wave was longer in cycles with three waves compared with that in cycles with four waves (P<0.05). The maximum diameter of the largest follicle was greater in the first wave and the ovulatory wave compared with that in other waves of the cycle (P<0.05). The regression phase of the largest follicle growing in the first wave was longer in cycles with three waves compared with that in cycles with four waves (4.44+/-0.4 vs. 3.4+/-0.4 d; P<0.05). The length of the life span, regression phase, and, although not significant in every case, FSH peak concentration and amplitude decreased across the cycle (P<0.05). We concluded that estrous cycles with three or four follicular waves were confined within the same length of cycle in WWF ewes. In this study, there were no apparent endocrine or follicular characteristics that could explain the regulation of the different number of follicular waves (three vs. four) during cycles of similar length.

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    • "Current information on follicular dynamics gives no particular physiological support for long-term treatments during the breeding season; therefore, they need to be re-evaluated. Sheep follicular dynamics has been characterized as having 3–4 follicular waves each one lasting 4–5 days ending in dominant follicles measuring 5–7 mm in diameter and persisting 2–3 days depending on the stage of the ovarian cycle (Bartlewski et al. 1999; Evans et al. 2000; Seekallu et al. 2010). Experience in cattle suggests that information on follicular dynamics needs to be considered to set up sound oestrous synchronization protocols for maximal fertility (for reviews Day et al. 2010; Lamb et al. 2010). "
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    ABSTRACT: ContentsThe study was aimed to assess the influence that short‐term progesterone treatments have on follicular dynamics, oestrus and ovulation in sheep. The treatment was tested thereafter in a field trial to assess its fertility after AI with fresh semen. In a first experiment, 12 ewes without CL were grouped to receive a new (n = 6) or used CIDR (n = 6) for 7 days and blood samples were obtained to follow plasma progesterone profiles. In a second experiment, 39 cycling ewes were synchronized by a 7‐day P4+PGF2α protocol using a new (n = 20) or a 7‐day used CIDR (n = 19). Half of both groups received 400 IU eCG and half remained untreated as controls. Ultrasound ovarian examination and oestrous detection were used to compare follicular dynamics, oestrus and ovulation in both groups. In a third experiment, 288 ewes in 3 farms were synchronized by the short‐term P4+PGF2α+eCG protocol and ewes were AI with fresh semen 24 h after oestrous detection. Lambing performance was used to test the fertility of the treatment. In Experiment 1, ewes with new inserts presented higher P4 concentration than ewes with used inserts throughout the sampling period (p 0.10). However, ewes treated with eCG show shorter interval to oestrus (p = 0.004) and tend to have larger mature CL (p = 0.06). In Experiment 3, oestrous presentation and lambing performance after AI with fresh semen was considered normal compared to published results. Results suggest that the oestrous synchronization protocol based on P4+PGF2α allows little control of follicular dynamics without compromising fertility after AI with fresh semen provided that eCG is added at the end of the treatment.
    Reproduction in Domestic Animals 04/2012; 47(6). DOI:10.1111/j.1439-0531.2012.01996.x · 1.52 Impact Factor
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    • "In sheep, ovarian follicular development occurs in a wave like pattern that is not interrupted during the seasonal anoestrous period or during pregnancy, with the three wave pattern being the most prominent during oestrus (Noel et al., 1993; Souza et al., 1996; Ravindra and Rawlings, 1997; Bartlewski et al., 1998). A transient increase in FSH peripheral concentration stimulates the emergence of a synchronous growth of a cohort of small follicles and, depending on intrinsic factors (breed), one or more follicles acquire dominance and grow to a diameter of >5 mm, preventing further development of the smaller follicles (Ravindra et al., 1994; Seekallu et al., 2010). Ovulation occurs from dominant follicles or these follicles regress and a new follicular wave commences. "
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    ABSTRACT: In modern agriculture, assisted reproductive technologies are being used for out of season oestrus induction, enhancement of reproductive performance and genetic improvement. In addition, they can have substantial contribution in preservation of endangered species or breeds, as well as in eradication programs of various diseases. While their applications are widespread in cattle, in small ruminants it is almost restricted to artificial insemination. The main limitations of a wider application in small ruminants are the naturally occurring anoestrus period, the variability of response to superovulatory treatments, the fertilisation failure and the need of surgery for collection and transfer of gametes and embryos. Nonetheless, during the last 30 years, considerable progress has been made in sheep and goat embryo technologies, especially in the fields of oestrus synchronisation, superovulation and in vitro embryo production. This paper reviews the status of assisted reproductive technologies in sheep, analysing the prospects offered by recent advances in in vivo and in vitro embryo production from mature and juvenile lambs.
    Animal reproduction science 01/2012; 130(3-4):152-61. DOI:10.1016/j.anireprosci.2012.01.009 · 1.51 Impact Factor
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    • "En este sentido , Seekallu y col. [29] concluyeron que, no hay características foliculares o endocrinas que puedan explicar la regulación del número de ondas foliculares (tres vs. cuatro) durante ciclos estrales de similar duración. Sin embargo, en vacas, la duración de la fase luteal parece determinar el número de ondas durante el ciclo. "
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    ABSTRACT: The follicular development was evaluated in ovine females during natural and prostaglandin-F2α (PG) induced estrous cycle. Ewes were randomly divided in two treatments (n=7/treatment): T1 with natural cycle and T2 synchronized with two injections of PG. From one day before PG injection until next ovulation, daily transrectal ultrasonography was done. All follicles >2 mm were assessed. During the interovulatory intervals, follicular growth and regression occurred in a wave like pattern (2-3 waves). The maximum diameter of the largest follicle of the first wave was greater in T1 (5.83 ± 0.31 mm) compared with T2 (5.0 ±0.1 mm; P<0.01), but there was no significant difference among the emergency day of largest follicle, during the growth phase of the follicular waves. The duration of the plateau phase in wave 2 differed between the two treatments (P<0.05) showing 0.83 ± 0.31 and 1.83 ± 0.17 d, for natural and synchronized treatment, respectively. Growth rate did not differ between treatments. Presence of new luteal tissue was detected on day 3 after ovulation. In conclusion, the follicular development was similar in female ovine during natural and PG induced estrous cycle.
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