Laparoscopy in the ewe: A photographic record of the ovarian activity of ewes experiencing normal or abnormal oestrous cycles

Oldham, C.M.; Lindsay, D. R.

doi:10.1016/0378-4320(80)90038-x

Cited by 73 publications

(43 citation statements)

References 3 publications

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“…The static and dynamic effects of nutrition on reproduction were analysed empirically in great descriptive detail without any significant advance in our knowledge of the underlying mechanisms. The seventies saw a number of important developments: first, the introduction of laparoscopy [15] that allowed the measurement of ovulation rate rather than litter size, second, the development of radioimmunoassays for the measurement of the blood concentrations of LH, FSH, progesterone and oestradiol and finally, the discovery of the acute effect of nutrition on ovulation rate [16]. Since then numerous mechanistic studies have improved our understanding of the physiological processes involved and now we are able to propose coherent testable hypotheses to explain how nutrition increases ovulation rate in sheep [17][18][19].…”

Section: Animal Modelsmentioning

confidence: 99%

A review of the effects of supplementary nutrition in the ewe on the concentrations of reproductive and metabolic hormones and the mechanisms that regulate folliculogenesis and ovulation rate

Scaramuzzi¹,

Campbell²,

Downing³

et al. 2006

Reprod. Nutr. Dev.

307

223

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-This paper discusses the phenomenon of nutritional flushing in ewes whereby increased nutrition stimulates folliculogenesis and ovulation rate. In addition the paper reviews recent findings on the effects of increased levels of nutrition on the blood concentrations of reproductive and metabolic hormones in the ewe and some of the intraovarian changes that take place in response to nutritional stimulation. Finally, in the paper, we propose a model of the physiological mechanism for the nutritional stimulation of folliculogenesis and we review how closely the model fits recent published and unpublished evidence examining the mechanism of flushing. Nutritional stimulation alters the blood concentrations of some metabolic hormones. By using short-term models of nutritional flushing, we have shown that as the blood concentrations of insulin and leptin increase that of growth hormone decreases while that of IGF-I appears unaffected by the nutritional flushing. Nutritional flushing also alters the blood concentrations of some reproductive hormones. Again, using the same model, we have shown that there is a transient increase in FSH and a decrease in oestradiol concentrations in the blood. The changes in oestradiol are particularly evident in the follicular phase of the oestrous cycle. In the ovary, the effect of nutrition is to stimulate folliculogenesis. These changes are associated with intra-follicular alterations in the insulin-glucose, IGF and leptin metabolic systems. The stimulation of these intra-follicular systems leads to a suppression in follicular oestradiol production. The consequence of these direct actions on the follicle is a reduced negative feedback to the hypothalamic-pituitary system and increased FSH secretion that leads to a stimulation of folliculogenesis.insulin / leptin / IGF-I / glucose / FSH / oestradiol

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Section: Animal Modelsmentioning

confidence: 99%

A review of the effects of supplementary nutrition in the ewe on the concentrations of reproductive and metabolic hormones and the mechanisms that regulate folliculogenesis and ovulation rate

Scaramuzzi¹,

Campbell²,

Downing³

et al. 2006

Reprod. Nutr. Dev.

307

223

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“…Coeslioscopy was carried out on D4 (experiment 1: groups I and II), D9, and 8-12 days following first oestrus (experiment 1: groups I and II, experiment 2: group V) in order to define the day of ovulation onset according to the criteria proposed by Oldham and Lindsay (1980) fig 2b) by a new luteal phase similar to those of normal cycles.…”

Section: Ovarian Dynamicsmentioning

confidence: 99%

Role of the uterus in early regression of corpora lutea induced by the ram effect in seasonally anoestrous Barbarine ewes

Lassoued¹,

Khaldi²,

Chemineau³

et al. 1997

Reprod. Nutr. Dev.

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Summary -The involvement of the uterus in early regression of corpora lutea induced by the ram effect was studied in seasonally anoestrous Barbarine ewes. In experiment 1, group I was only submitted to the male effect (control, n = 15) while group II (n = 14) was injected every 12 h with flunixin meglumine, a PGF2a synthetase inhibitor (finadyne), from day 3 to day 6 (day 0: day of ram introduction). The preovulatory LH surge appeared at the same time (around 21 h after ram introduction) in both groups. Finadyne treatment significantly decreased 13-14-dihydro-15-keto-PGF2a (PGFM) pulses ( 1.3 ± 0.3 versus 0.4 ± 0.2; P < 0.05), the number of short cycles (50 versus 14%, P < 0.05), and provided a single peak of oestrus, 15-16 days after the introduction of the rams, instead of between day 14 and day 23 (P < 0.01 In experiment 2, 17 hysterectomized ewes were allocated into two groups: group III (n = 8) was injected with oil and group IV (n = 9) received an intramuscular injection of 20 mg of progesterone immediately before introduction of rams. An additional group of intact ewes was used as control (group V, n = 9). Hysterectomy did not affect the ovulation response to the ram effect, but completely suppressed short cycles (0 versus 78% , P < 0.001). The preovulatory LH surge was delayed in hysterectomized females (36.0 ± 14.1 versus 16.6 ± 11.4 h; P < 0.004). Treatment with progesterone significantly (P < 0.01) increased the interval between introduction of rams and the preovulatory LH surge. In conclusion, suppression of short cycles by hysterectomy and an inhibitor of PGF2a synthetase suggest that the uterus is essential for determining the lifespan of ram-induced corpora lutea and that premature release of PGF2a is the cause of early luteal regression. The hypothesis that lower secretion of progesterone before D5 could be the initial cause of the premature induction of the luteolytic signal is discussed.

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“…In addition, one experiment investigated whether efficacy of the 'ram effect' could be improved by re-isolating ewes from rams for the period between first ovulation and anticipated oestrus. (Oldham & Martin, 1978;Oldham & Lindsay, 1980). Briefly, CL were defined as having a normal life-span if they were present at both the Day-5 and Day-12 laparoscopy.…”

Section: Introductionmentioning

confidence: 99%

Progesterone priming and age of ewe affect the life-span of corpora lutea induced in the seasonally anovulatory Merino ewe by the 'ram effect'

Oldham¹,

Pearce²,

Sj³

1985

Reproduction

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Laparoscopy in the ewe: A photographic record of the ovarian activity of ewes experiencing normal or abnormal oestrous cycles

Cited by 73 publications

References 3 publications

A review of the effects of supplementary nutrition in the ewe on the concentrations of reproductive and metabolic hormones and the mechanisms that regulate folliculogenesis and ovulation rate

A review of the effects of supplementary nutrition in the ewe on the concentrations of reproductive and metabolic hormones and the mechanisms that regulate folliculogenesis and ovulation rate

Role of the uterus in early regression of corpora lutea induced by the ram effect in seasonally anoestrous Barbarine ewes

Progesterone priming and age of ewe affect the life-span of corpora lutea induced in the seasonally anovulatory Merino ewe by the 'ram effect'

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