Effects of a Single Injection of LHRH on the Response of Anestrous Ewes to the Introduction of Rams1

Gómez-Brunet, A.; Inskeep, E. K.

doi:10.2527/jas1984.592277x

Cited by 32 publications

(8 citation statements)

References 25 publications

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“…Progesterone concentrations were determined in duplicate in 200 μl aliquots of plasma (following extraction with 3 ml fresh hexane) according to the radioimmunoassay method of López‐Sebastián et al. (1984).…”

Section: Methodsmentioning

confidence: 99%

Evidence that Refractoriness to Long and Short Daylengths Regulates Seasonal Reproductive Transitions in Mediterranean Goats

Gómez-Brunet

Santiago-Moreno

Toledano-Dı́az

2010

Reprod Domestic Animals

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Two experiments were performed to assess the role of refractoriness to long and short daylengths in the timing of seasonal reproductive transitions in Mediterranean Malagueña goats. In the first experiment, intact adult does were either maintained under natural photoperiod conditions (NP; n = 5) or exposed to a constant long day photoperiod (LD - 16 h light/day; n = 5) from June to December 2005. In the second experiment, does were maintained either under NP conditions (n = 5) or received a series of subcutaneous melatonin implants (MI) from December 2005 to June 2006 to mimic a short day signal (n = 5). In both experiments, ovulatory activity was assayed by determining progesterone concentrations in blood samples collected twice per week. The onset of seasonal ovulatory activity did not differ (p > 0.05) between the LD and NP does (3 October ±5 days and 23 September ±3 days respectively). The simulated short days did not modify (p > 0.05) the timing of the end of ovulatory activity. The MI does become anoestrus at the same time (1 March ±9 days) as their NP counterparts (23 February ±8 days). These results indicate that, in Malagueña does, the onset and offset of anoestrus are not driven by photoperiod changes but appear to be the result of long and short day refractoriness respectively. An endogenous circannual rhythm may therefore be involved in regulating seasonal reproductive changes in these animals.

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Section: Methodsmentioning

confidence: 99%

Evidence that Refractoriness to Long and Short Daylengths Regulates Seasonal Reproductive Transitions in Mediterranean Goats

Gómez-Brunet

Santiago-Moreno

Toledano-Dı́az

2010

Reprod Domestic Animals

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“…The plasma progesterone concentration was determined in duplicate in 200-ll aliquots of plasma (following extraction with 3 ml fresh hexane) according to the radioimmunoassay method of López-Sebastián et al [31]. The assay sensitivity was 0.12 ng/ml, and the intra-and interassay coefficients of variation were 7.4% and 10.6%, respectively.…”

Section: Hormone Assaysmentioning

confidence: 99%

Endogenous Circannual Cycles of Ovarian Activity and Changes in Prolactin and Melatonin Secretion in Wild and Domestic Female Sheep Maintained under a Long-Day Photoperiod1

Gómez-Brunet¹,

Santiago-Moreno²,

Campo³

et al. 2008

Biology of Reproduction

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The present study examines the ovulatory activity of wild and domesticated ewes subjected to either a constant photoperiod of long days (16L:8D) or natural changes in daily photoperiod for 16 mo. The aim was to determine whether an endogenous reproductive rhythm controls seasonal reproductive activity in these sheep, and how the photoperiod might affect this. The effects of long-day photoperiods on long-term changes in prolactin and melatonin secretion were also evaluated. The two species showed changes in reproductive activity under the constant photoperiod conditions, suggesting the existence of an endogenous rhythm of reproduction. This rhythm was differently expressed in the two types of ewe (P < 0.05), with the domestic animals exhibiting much greater sensitivity to the effects of long days. A circannual rhythm of plasma prolactin concentration was also seen in both species and under both photoperiod conditions, although in both species the amplitude was always lower in the long-day animals (P < 0.01). The duration of the nocturnal melatonin plasma concentrations reflected the duration of darkness in both species and treatments. The peak melatonin concentration did not differ between seasons either under natural or long-day photoperiods.

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“…Thereafter, the plasma was stored at -20 ºC until being assayed for hormone concentrations. Progesterone concentration was determined in individual plasma by radioimmunoassay as Embryo degeneration in superovulated ewesdescribed by Lopez-Sebastian et al [13]. Sensitivity was 0.06 ng·mL -1 and the interand intra-assay variation coefficients were 13.6 and 10.4%, respectively.…”

Section: Hormonal Assaysmentioning

confidence: 99%

Influence of maternal environment on the number of transferable embryos obtained in response to superovulatory FSH treatments in ewes

González-Bulnes¹,

García-García²,

Castellanos

et al. 2003

Reprod. Nutr. Dev.

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-In a first experiment, embryo viability was estimated after recovery in the uterus or the oviduct of 70 Manchega ewes following a treatment of superovulation with decreasing doses of OVAGEN TM . Fewer viable embryos (5.6 ± 0.9 vs. 8.3 ± 0.8, P < 0.05) and more degenerative embryos (31.3% vs. 6.8%, P < 0.005) were obtained from the uterus than from the oviduct respectively. In a second experiment performed on 14 ewes, embryo viability was analyzed in relation to the follicular population estimated by ultrasonography (follicles ≥ 2 mm) at the first FSH administration. Progesterone (P4) and oestradiol 17β (E2) concentrations were also determined from the beginning of the superovulation treatment to the recovery of the embryos. The number of viable embryos (4.3 ± 1.4) was positively correlated (r = 0.824) with of 2-4 mm diameter follicles (P < 0.05), and with E2 concentrations at -12 h (r = 0.891, P < 0.01) , 0 h (r = 0.943, P < 0.0001) and +24 h (r = 0.948, P < 0.05) from estrus detection. Prolonged high levels of E2 up to 72 h with low levels of P4 on days 3 and 4 after estrus had a negative (P < 0.05) effect on embryo viability. These results indicate that ovarian response to superovulatory protocols is related to the individual variations in the number of follicles of 2-4 mm at the start of FSH treatment, and that embryo viability is conditioned by the steroid patterns during the time spent in the genital tract of the super-ovulated ewes.embryo viability / ewe / follicular status / super-ovulation / steroid Reprod. Nutr. Dev. 43 (2003) 17-28 17

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Effects of a Single Injection of LHRH on the Response of Anestrous Ewes to the Introduction of Rams1

Cited by 32 publications

References 25 publications

Evidence that Refractoriness to Long and Short Daylengths Regulates Seasonal Reproductive Transitions in Mediterranean Goats

Evidence that Refractoriness to Long and Short Daylengths Regulates Seasonal Reproductive Transitions in Mediterranean Goats

Endogenous Circannual Cycles of Ovarian Activity and Changes in Prolactin and Melatonin Secretion in Wild and Domestic Female Sheep Maintained under a Long-Day Photoperiod1

Influence of maternal environment on the number of transferable embryos obtained in response to superovulatory FSH treatments in ewes

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