Induction of ovarian cystic follicles in sheep

Christman, Shelly A.; Bailey, Michael T.; Head, William A.; Wheaton, J. E.

doi:10.1016/s0739-7240(00)00077-1

Cited by 17 publications

(19 citation statements)

References 40 publications

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“…However in an earlier study, Heuer et al [91] observed that a high fat/protein ratio, and, therefore, a more severe NEB, increased the risk of cyst occurrence. Data in sheep also suggest that an increased mobilisation of body reserves, indicative for a deeper NEB, is linked with the occurrence of cystic follicles [76]. Although a concensus is lacking, we conclude from the literature that a link seems to exist between COF and the magnitude and/or duration of the NEB.…”

Section: Predisposing Factors For Cofmentioning

confidence: 56%

“…However hypersecretion of LH does not seem to be involved in cyst formation, but it may play a role in cyst persistence [75]. Data obtained in sheep also dismiss an increased LH secretion as a primary cause of COF [76].…”

Section: Hypothalamic-pituitary Dysfunctionmentioning

confidence: 88%

“…However, insulin insufficiency rather than insulin resistance has been observed in COF cows [116], indicating an altered interaction between glucose and insulin at the pancreatic level. In addition, in ewes it was not possible to induce cyst formation through the establishment of a state of insulin resistance [76]. Conclusively, IGF-1 and insulin are important stimulators of follicle growth and based on the limited number of publications on the subject, low concentrations of one or both hormones may contribute to the formation of COF (Fig.…”

Section: Predisposing Factors For Cofmentioning

confidence: 99%

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Aetiology and pathogenesis of cystic ovarian follicles in dairy cattle: a review

2006

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-Cystic ovarian follicles (COF) are an important ovarian dysfunction and a major cause of reproductive failure in dairy cattle. Due to the complexity of the disorder and the heterogeneity of the clinical signs, a clear definition is lacking. A follicle becomes cystic when it fails to ovulate and persists on the ovary. Despite an abundance of literature on the subject, the exact pathogenesis of COF is unclear. It is generally accepted that disruption of the hypothalamo-pituitary-gonadal axis, by endogenous and/or exogenous factors, causes cyst formation. Secretion of GnRH/LH from the hypothalamus-pituitary is aberrant, which is attributed to insensitivity of the hypothalamus-pituitary to the positive feedback effect of oestrogens. In addition, several factors can influence GnRH/LH release at the hypothalamo-pituitary level. At the ovarian level, cellular and molecular changes in the growing follicle may contribute to anovulation and cyst formation, but studying follicular changes prior to cyst formation remains extremely difficult. Differences in receptor expression between COF and dominant follicles may be an indication of the pathways involved in cyst formation. The genotypic and phenotypic link of COF with milk yield may be attributed to negative energy balance and the associated metabolic and hormonal adaptations. Altered metabolite and hormone concentrations may influence follicle growth and cyst development, both at the level of the hypothalamus-pituitary and the ovarian level.cystic ovarian follicles / pathogenesis / hypothalamus-pituitary / ovary / negative energy balance

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Section: Predisposing Factors For Cofmentioning

confidence: 56%

Section: Hypothalamic-pituitary Dysfunctionmentioning

confidence: 88%

Section: Predisposing Factors For Cofmentioning

confidence: 99%

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Aetiology and pathogenesis of cystic ovarian follicles in dairy cattle: a review

2006

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“…(a) Maximum LH value: the highest plasmatic LH concentration (ng/ml) found in consecutive samples obtained every 4 h through 24 h following the OE; (b) Basal LH value: the average of plasmatic LH concentration (ng/ml) quantified in all plasmatic samples, excluding the maximum LH value and the values immediately preceding and following; (c) Time of preovulatory LH peak: the time of the maximum LH rise, if there was, at least, a fivefold amount of the basal LH value and at least 5 ng/ml, just as it was proposed for ewes by Christman et al (2000).…”

Section: Animalsmentioning

confidence: 99%

Time of ovulation in nulliparous and multiparous goats

Simões

Baril

Almeida

et al. 2008

Animal

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Fifteen nulliparous and nine multiparous Serrana goats were used, through two successive oestrous cycles, in order to characterize their ovulation time with regard to the number of ovulations after induced and natural oestrus during the breeding season. The onset of oestrus was detected by the amount of vasectomized bucks after oestrus synchronization with prostaglandin, given 10 days apart, and in the following two expected natural oestrus. The preovulatory LH peak was determined from blood samples collected 0, 4, 8, 12, 16, 20 and 24 h after onset of oestrus. A transrectal ovarian ultrasound scanning was performed 20, 24, 28, 32, 36, 40, 44 and 60 h after onset of oestrus, for the detection of ovulations by means of the disappearance of large follicles (.4 to 5 mm). Single ovulations were observed in 76% of oestrous periods in nulliparous goats and in 18% of nulliparous goats. The onset of oestrus to LH peak interval was lower in nulliparous (12.1 6 0.9 h, n 5 38) than in multiparous (15.6 6 1.0 h, n 5 22, P , 0.05) goats with no oestrus interaction effects (P . 0.05). The LH peak to first ovulation interval was higher after natural (18.9 6 0.7 h, n 5 36) than after induced (15.8 6 1.2 h, n 5 24, P , 0.05) oestrus. The onset of oestrus to total ovulation interval was influenced by parity (P , 0.01) and oestrus type (P , 0.05) with a length of 30.1 6 1.1 h (n 5 15) and 33.4 6 1.5 h (n 5 9) for induced oestrus of nulliparous and multiparous goats, respectively, and 32.5 6 1.0 h (n 5 23) and 36.5 6 1.1 h (n 5 13) for natural oestrus of nulliparous and multiparous goats, respectively. The onset of oestrus to first ovulation interval was not influenced by parity, but an interval of 8.0 6 1.6 h was observed between the first and second ovulations in polyovulatory oestrus. Consequently, nulliparous goats that are predominantly monovular ovulate earlier than multiparous goats that are predominantly polyovulatory. In conclusion, significant differences occurred in the number and time of ovulations between nulliparous and multiparous goats. More research is necessary for a deeper understanding of the mechanisms regulating monovularory and polyovulatory oestrous cycles regarding the parity of goats.

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“…Introduction Follicular cysts have been reported in many mammalian species, including cattle (Roberts 1971, Kesler & Garverick 1982, swine (Heinonen et al 1998), dogs (Arbeiter 1993, rabbits (Lopez-Bejar et al 1998), rats (Brawer et al 1986), mares (McCue & Squires 2002), sheep (Christman et al 2000), elephants (Brown et al 1999) and women (Stein & Leventhal 1935). In cattle, this condition is characterized by large (generally $25 mm in diameter) anovular structures that persist on the ovary for at least 10 days in the absence of a corpus luteum (CL) (Roberts 1971).…”

Section: Reproduction (2005) 129 737-745mentioning

confidence: 99%

Follicular cysts occur after a normal estradiol-induced GnRH/LH surge if the corpus hemorrhagicum is removed

Gümen

Wiltbank²

2005

Reproduction

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The pathophysiology underlying follicular cysts appears to be lack of an estradiol (E 2 )-induced GnRH/LH surge due to hypothalamic insensitivity to E 2 . In addition, progesterone (P 4 ) can cause animals with follicular cysts to resume normal cyclicity and normal hypothalamic responsiveness to E 2 . We postulated that follicular cysts may be a pathological manifestation of a physiological state that cows, and possibly other species, go through during the normal estrous cycle but the rise in P 4 following ovulation induces them back to normal hypothalamic responsiveness to E 2 . Based on this hypothesis, we expected that removal of the ovary containing the corpus hemorrhagicum would prevent the normal rise in P 4 following ovulation and induce development of follicular cysts. Cows (n 5 24) on day 7 of the estrous cycle were treated with prostaglandin F 2a (PGF 2a ) and time of ovulation was detected by ovarian ultrasonography every 8 h. Immediately following detection of ovulation, cows were randomly but unequally assigned to have the ovary containing the corpus hemorrhagicum removed (TRT; n 5 16) or the ovary opposite to the corpus hemorrhagicum removed (CON; n 5 8). Cows were subsequently evaluated by daily ultrasound and blood sampling to determine follicular dynamics. Ovulation was detected at 93.7 6 4.5 h after PGF 2a injection. All CON cows had a normal estrous cycle length (22.0 6 0.6 days) after ovariectomy (OVX). Half of the TRT cows became anovular (TRT-ANO; n 5 8) after OVX with large anovular follicles developing on the ovary (maximal size, 25.4 6 1.4 mm; range, 20-32 mm). However, eight TRT cows ovulated (TRT-OV; n 5 8) 7.3 6 0.6 days after OVX. Control cows had a normal P 4 rise after ovulation. Removal of the newly formed corpus hemorrhagicum prevented the rise in circulating serum P 4 in TRT-ANO cows throughout the 25-day experimental period. The TRT-OV cows had a delayed increase in circulating P 4 but it was normal in relation to time of ovulation. Serum E 2 concentrations were similar among groups (TRT-OV, TRT-ANO and CON cows) until 7 days after OVX. Serum E 2 concentrations then decreased in TRT-OV and CON cows but remained elevated (> 5 pg/ml) in TRT-ANO cows. Thus, the endogenous increase in circulating E 2 that induces the GnRH/LH surge and estrus is sufficient to induce cows into a physiological state that resembles follicular cysts if it is not followed by increased circulating P 4 . Reproduction (2005) 129 737-745Introduction Follicular cysts have been reported in many mammalian species, including cattle (Roberts 1971, Kesler & Garverick 1982, swine (Heinonen et al. 1998), dogs (Arbeiter 1993, rabbits (Lopez-Bejar et al. 1998), rats (Brawer et al. 1986), mares (McCue & Squires 2002), sheep (Christman et al. 2000), elephants (Brown et al. 1999) and women (Stein & Leventhal 1935). In cattle, this condition is characterized by large (generally $25 mm in diameter) anovular structures that persist on the ovary for at least 10 days in the absence of a corpus luteum (CL) (Roberts 1...

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Induction of ovarian cystic follicles in sheep

Cited by 17 publications

References 40 publications

Aetiology and pathogenesis of cystic ovarian follicles in dairy cattle: a review

Aetiology and pathogenesis of cystic ovarian follicles in dairy cattle: a review

Time of ovulation in nulliparous and multiparous goats

Follicular cysts occur after a normal estradiol-induced GnRH/LH surge if the corpus hemorrhagicum is removed

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