Hormonal and follicular relationships in ewes of high and low ovulation rates

Cahill, L. P.; Saumande, J.; Ravault, J. P.; Blanc, Michel; Thimonier, J.; Mariana, J. C.; Mauléon, P.

doi:10.1530/jrf.0.0620141

Cited by 107 publications

(57 citation statements)

References 18 publications

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“…(The amount of LH discharged was not related to ovulation rate.) The physiological significance of this phenomenon was questioned by Cahill et al (1981) in their study of the Romanov breed, since the number of ovulatory follicles is already decided by this time. In any event the Booroola did not conform to the pattern of other prolific sheep in this regard with both Booroola and controls having an LH discharge about 4· 5 h after the onset of oestrus (Table 8).…”

Section: Role Of Lh and Lh Pulse Frequencymentioning

confidence: 99%

“…When FSH concentrations were compared over broad time periods (PG to onset of oestrus; during oestrus; from end of oestrus for 24 h), there were no significant differences between the genotypes. This type of study was repeated in more detail by Cahill et al (1981) in the normal oestrous cycle, and the FSH profiles were aligned with respect to the pre-ovulatory LH discharge. In this case Romanov ewes had a significantly (P<O· 05) greater day 2 FSH peak than another breed.…”

Section: Role Of Fsh In Regulation Of Ovulation Ratementioning

confidence: 99%

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Reproductive Biology of the Booroola Merino Sheep

Bm¹

1984

Aust. Jnl. Of Bio. Sci.

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This paper reviews the genetic and physiological characteristics of the Booroola Merino, one of the four most prolific sheep breeds in the world, and which was acquired by CSIRO in 1958 from a commercial sheep property, 'Booroola', Cooma, N.S.W. The exceptional prolificacy of this genotypee.g. mean flock ovulation rate in 1982 of 4·2 (range 1-10) and mean litter size of 2· 5 (range 1-7)-is largely attributable to a single gene (F) of uncertain origin which increases ovulation rate. Crosses of the Booroola with other Merinos produce progeny which have a 47-87% increase in ovulation rate, a 45-56% increase in litter size at birth, and a 1-33% reduction in lamb survival relative to control Merinos. This represents a 16-37% increase in the number of lambs weaned per ewe joined in favour of the Booroola crosses.The exact site of action of the F gene is not well established, although it is expressed primarily at the ovary, where more than the normal number of follicles mature and ovulate each oestrous cycle. This may result from some abnormality of the Booroola follicle itself or it may reflect differences in Booroola gonadotrophin secretion. There is some evidence that Booroola ewes have elevated plasma concentrations of follicle stimulating hormone (FSH) early in life and during the oestrous cycle, and that FSH concentrations in the pituitary gland and urine of the adult ewe are also high. These elevated FSH levels in the adult are attributed to an ovarian feedback deficiency, probably because the inhibin content of the Booroola ovary is only one-third that of normal Merino ovaries. The low inhibin content appears to be due to Booroola follicles having significantly fewer granulosa cells than control Merinos. Analogous studies of the prolific D'man sheep of Morocco point to FSH as the main correlate of prolificacy.The testis growth rate, testis size and total daily production of spermatozoa of the Booroola ram are similar to those of normal Merinos, as also are the endocrine characteristics of adult rams. The Booroola gene's expression is evidently sex-limited. Several theories concerning the mode of action of the F gene are being tested.

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Section: Role Of Lh and Lh Pulse Frequencymentioning

confidence: 99%

Section: Role Of Fsh In Regulation Of Ovulation Ratementioning

confidence: 99%

Reproductive Biology of the Booroola Merino Sheep

Bm¹

1984

Aust. Jnl. Of Bio. Sci.

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“…Similar breed differences in the concentration of E 2 before the surge have been observed during the breeding season and have often been linked with the prolificity of the breed (Land et al 1976, Cahill et al 1981. In one study using both intact and ovariectomised ewes, Ben Saïd et al (2007) showed that Romanov ewes, a breed that has multiple ovulations, require higher concentrations of E 2 and for a longer duration for the induction of a LH surge than IF ewes.…”

Section: Discussionmentioning

confidence: 75%

“…The LH surge occurs only after a period of prolonged exposure to the above threshold concentrations of E 2 (Corker et al 1969, Karsch et al 1973, 1979, Smith et al 1975, Hauger et al 1977. In sheep, the characteristics of the relationship between the preovulatory rise in systemic concentrations of E 2 and the onset of the LH surge, and presumably of GNRH, varies among breeds (Land et al 1976, Cahill et al 1981, Ben Saïd et al 2007.…”

Section: Introductionmentioning

confidence: 99%

Plasma and ovarian oestradiol and the variability in the LH surge induced in ewes by the ram effect

Fabre-Nys¹,

Chanvallon²,

Debus³

et al. 2015

Reproduction

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The proportion of anoestrous ewes ovulating after exposure to a sexually active ram is variable mainly due to whether an LH surge is induced. The aim of this study was to determine the role of oestradiol (E 2 ) in the ram-induced LH surge. In one study, we measured the plasma concentrations of E 2 in ewes of different breeds before and after the 'ram effect' and related these patterns to the presence and latency of the LH surge, while another compared ovarian responses with the 'ram effect' following exposure to rams for 2 or 12 h. In all ewes, the concentration of E 2 increased 2-4 h after rams were introduced and remained elevated for 14.5G0.86 h. The quantity of E 2 secreted before the LH surge varied among breeds as did the mean concentration of E 2 . The granulosa cells of IF ewes collected after 12 h exposure to rams secreted more E2 and progesterone and had higher levels of StAR than the 2 h group but in MV ewes there was no differences between these groups for any of these parameters. These results demonstrate that the LH surge induced by the rams is a result of increased E 2 secretion associated with increased levels of STAR in granulosa cells and that these responses varied among breeds. The results suggest that the variable occurrence of a LH surge and ovulation may be the result of variable ovarian responses to the 'ram effect' and insensitivity of the hypothalamus to the E 2 -positive feedback signal. Free French abstract: A French translation of this abstract is freely available at

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“…The use of gonadotrophic pituitary extracts for ovarian hyperstimulation enhances embryo production (Martemucci et al, 1988;Jabbour and Evans, 1991). Taking into account the physiological hormonal pattern from luteal regression and preovulatory peak in LH (Cahill et al, 1981), several studies have demonstrated that the daily FSH/LH ratio during treatment appears to be important in the superovulatory response in small ruminants for in vivo embryo production (Chupin et al, 1987;Baril et al, 1989;Martemucci et al, 1996;D'Alessandro et al, 1997).…”

Section: Introductionmentioning

confidence: 99%

Use of purified FSH and LH for embryo production, cryopreservation by conventional freezing or vitrification and transfer of embryos in dairy ewes

D’Alessandro¹,

Martemucci²

2003

Italian Journal of Animal Science

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Three experiments were carried out with the aim of evaluating the efficiency of techniques of in vivo production, storage and transfer of embryos in dairy sheep. Experiment I -For embryo production, thirty-one ewes were synchronized with FGA (vaginal sponges, 40 mg, 9 d) and PGF2α (ICI; 50 µg, 7 th d), and subdivided into three groups corresponding to the following superovulatory treatments over 3 days with purified gonadotrophic preparations: A) control, FSH/LH ratio = 1 (250 IU p-FSH : 250 UI p-LH); B) FSH/LH ratio = 2 (250 IU p-FSH : 125 IU p-LH) and daily FSH/LH ratio of 3.4 -1.7 -0.8 in the 3 days of treatment, respectively; C) FSH/LH ratio = 2 (250 IU p-FSH : 125 IU p-LH) and daily FSH/LH ratio of 5.0 -1.0 -0.3. On the 7 th day after oestrus and mating, ovarian response and embryo production were evaluated. Experiment II -Three freezing methods were evaluated based upon post-thaw embryo quality: CF) conventional slow freezing by 1.5 M ethylene glycol (EG); V-1) one-step vitrification based on exposure of the embryos to one solution (EG 7.15 M + ficoll 2.5 mM); V-3) vitrification in three steps, corresponding to three solutions at increasing concentration of glycerol (GLY) and EG (GLY 1.4 M; GLY 3.4 M + EG 1.4 M; GLY 4.6 M + EG 3.4 M). V-1) and V-3) frozen embryos were directly plunged in liquid nitrogen. At thawing, embryo viability was evaluated on the basis of morphological features. Experiment III -For embryo transfer, a total of 26 recipient ewes were synchronized with donors. On the 7 th d from oestrus, 11 recipient ewes received fresh embryos (Group FE -control) and 15 recipients received vitrified-thawed embryos (Group VTE). Each recipient received 2 embryos. Superovulatory treatment B) significantly advanced the onset of oestrus compared to the control (27.3 vs 34.7 h; P<0.05). Ovulation rate did not differ among the groups (6.5 to 10.8). Transferable embryos in Group B) (7.2) resulted similar to Group A) (5.3) and significantly (P<0.05) different when compared to Group C) (3.2). V3-method resulted in the highest (P<0.01) transferable embryos (74.5%) compared to CF-and V1-methods. After transfer, in FE and VTE recipient ewes were comparable in fertility rates (72.7 vs 73.3%; P>0.05) and embryo survival (63.6 vs 56.7%; P>0.05). In conclusion, the results demonstrated that treatments B) and C) did not improve superovulatory response compared to A); for embryo cryopreservation the V3 method can successfully be used for embryo transfer in ewes. (27,3 vs 34,7 ore; P<0,05). Il tasso di ovulazione non è stato influenzato dal trattamento (6,5 -10,8; P>0,05). La produzione di embrioni trasferibili registrata nel Gruppo B) (7,2) è stata similare al controllo (Gruppo A, 5,3) e maggiore rispetto al trattamento C) (3,2; P<0,05

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Hormonal and follicular relationships in ewes of high and low ovulation rates

Cited by 107 publications

References 18 publications

Reproductive Biology of the Booroola Merino Sheep

Reproductive Biology of the Booroola Merino Sheep

Plasma and ovarian oestradiol and the variability in the LH surge induced in ewes by the ram effect

Use of purified FSH and LH for embryo production, cryopreservation by conventional freezing or vitrification and transfer of embryos in dairy ewes

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