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

Lassoued, N.; Khaldi, G.; Chemineau, Philippe; Cognie, Y.; Thimonier, J.

doi:10.1051/rnd:19970507

Cited by 22 publications

(13 citation statements)

References 29 publications

(39 reference statements)

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“…Additionally, inhibition of PGF synthesis with indomethacin reduced, but did not completely suppress, short cycles (Acritopoulou & Haresign 1980). Interestingly, in our study, the level of the receptor for PGF2aR, which mediates luteolysis, was actually lower in the short-cycle group, and in conjunction with the unchanged concentrations of PGFM, these data contradict the above findings (Acritopoulou & Haresign 1980, Chemineau et al 1993, Lassoued et al 1997 and suggest that the normal luteolytic pathway is not active during the short cycle. Obviously, this is a serious discrepancy that can only be resolved by further experimentation.…”

Section: Discussioncontrasting

confidence: 82%

“…Hysterectomised ewes were reported to have a very few or no short cycles (Chemineau et al 1993, Lassoued et al 1997, findings that support the premature luteolysis hypothesis. Additionally, inhibition of PGF synthesis with indomethacin reduced, but did not completely suppress, short cycles (Acritopoulou & Haresign 1980).…”

Section: Discussionmentioning

confidence: 74%

“…This model proposes poor follicular quality, leading to an insufficient proportion of large luteal cells resulting in lower progesterone production, all culminating in premature PG-stimulated luteolysis. There is evidence to suggest that uterine PG is involved in short cycles (Acritopoulou & Haresign 1980, Chemineau et al 1993, Lassoued et al 1997, lending support to this hypothesis. There is virtually no published evidence to support the failure of the luteinisation model; nevertheless, it remains an obvious and attractive alternative model.…”

Section: Introductionmentioning

confidence: 84%

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Short oestrous cycles in sheep during anoestrus involve defects in progesterone biosynthesis and luteal neovascularisation

Brown

Nys²,

Cognié³

et al. 2014

Reproduction

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Anoestrous ewes can be induced to ovulate by the socio-sexual, 'ram effect'. However, in some ewes, the induced ovulation is followed by an abnormally short luteal phase causing a so-called 'short cycle'. The defect responsible for this luteal dysfunction has not been identified. In this study, we investigated ovarian and uterine factors implicated in male-induced short cycles in anoestrous ewes using a combined endocrine and molecular strategy. Before ovulation, we were able to detect a moderate loss of thecal expression of steroid acute regulatory protein (STAR) in ewes that had not received progesterone priming (which prevents short cycles). At and following ovulation, we were able to identify a significant loss of expression of genes coding key proteins involved in the biosynthesis of progesterone (STAR, CYP11A1 and HSD3B1 (HSD3B)) as well as genes coding proteins critical for vascular development during early luteal development (VEGFA and KDR (VEGFR2)), suggesting dysfunction in at least two pathways critical for normal luteal function. Furthermore, these changes were associated with a significant reduction of progesterone production and luteal weight. Additionally, we cast doubt on the proposed uterus-mediated effect of prostaglandin F2a (PGF2a) as a cause of short cycles by demonstrating the dysregulation of luteal expression of the PGF receptor, which mediates the luteal effects of PGF2a, and by finding no significant changes in the circulating concentrations of PGFM, the principal metabolite of PGF2a in ewes with short cycles. This study is the first of its kind to examine concurrently the endocrine and molecular events in the follicular and early luteal stages of the short cycle. Free French abstractA French translation of this abstract is freely available at

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Section: Discussioncontrasting

confidence: 82%

Section: Discussionmentioning

confidence: 74%

Section: Introductionmentioning

confidence: 84%

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Short oestrous cycles in sheep during anoestrus involve defects in progesterone biosynthesis and luteal neovascularisation

Brown

Nys²,

Cognié³

et al. 2014

Reproduction

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“…In Prealpes and Barbarine ewes, hysterectomy does not modify the percentage of ewes ovulating after the introduction of rams, and completely prevented luteolysis of ram-induced CL compared to control ewes: 0 vs. 50% in Prealpes and 78% in Barbarine ewes, respectively [19,44].…”

Section: Importance Of the Uterus And Prostaglandins And Of The Ovarmentioning

confidence: 88%

“…The i.m. injection of a more potent PGF2 alpha synthetase inhibitor (finadyne) every 12 h from D3 to D6, significantly decreased 13-14-dihydro-15-keto-PGF2 α (PGFM) pulses (1.3 vs. 0.4 pulses), and reduced the frequency of short cycles (50 vs. 14% [44]). Thus, as early as D3, that is when CL are just sensitive to PGF [46], a part of the females have their male-induced CL which is luteolysed by uterine prostaglandins.…”

Section: Importance Of the Uterus And Prostaglandins And Of The Ovarmentioning

confidence: 99%

Male-induced short oestrous and ovarian cycles in sheep and goats: a working hypothesis

et al. 2006

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-The existence of short ovulatory cycles (5-day duration) after the first male-induced ovulations in anovulatory ewes and goats, associated or not with the appearance of oestrous behaviour, is the origin of the two-peak abnormal distribution of parturitions after the "male effect". We propose here a working hypothesis to explain the presence of these short cycles. The male-effect is efficient during anoestrus, when follicles contain granulosa cells of lower quality than during the breeding season. They generate corpora lutea (CL) with a lower proportion of large luteal cells compared to small cells, which secrete less progesterone, compared to what is observed in the breeding season cycle. This is probably not sufficient to block prostaglandin synthesis in the endometrial cells of the uterus at the time when the responsiveness to prostaglandins of the new-formed CL is initiated and, in parallel, to centrally reduce LH pulsatility. This LH pulsatility stimulates a new wave of follicles secreting oestradiol which, in turn, stimulates prostaglandin synthesis and provokes luteolysis and new ovulation(s). The occurrence of a new follicular wave on days 3-4 of the first male-induced cycle and the initiation of the responsiveness to prostaglandins of the CL from day 3 of the oestrous cycle are probably the key elements which ensure such regularity in the duration of the short cycles. Exogenous progesterone injection suppresses short cycles, probably not by delaying ovulation time, but rather by blocking prostaglandin synthesis, thus impairing luteolysis. The existence, or not, of oestrous behaviour associated to these ovulatory events mainly varies with species: ewes, compared to does, require a more intense endogenous progesterone priming; only ovulations preceded by normal cycles are associated with oestrous behaviour. Thus, the precise and delicate mechanism underlying the existence of short ovulatory and oestrous cycles induced by the male effect appears to be dependent on the various levels of the hypothalamo-pituitary-ovario-uterine axis.male-effect / ovulation / corpus luteum / cycle / oestrus / uterus

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Merits of the fat-tailed Barbarine sheep raised in different production systems in Tunisia: digestive, productive and reproductive characteristics

Salem

Lassoued

Rekik³

2011

Trop Anim Health Prod

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Barbarine sheep is the dominant breed in Tunisia. This fat-tailed breed present in all production systems is characterised by metabolic and digestive adaptation to the contrasting environment conditions prevailing in the country (heat stress, water deprivation, salinity etc.). The fat tail (1.5 to 7 kg) is an energy reservoir that is used in periods of feed scarcity. Moreover, the rumen of this breed harbours a microflora enabling it to valorize low-quality roughages and native range vegetation. Barbarine sheep could make benefit from a wide range of local feed resources like fodder shrubs (e.g. cactus and oldman saltbushes), tannin-containing shrubs (e.g. Acacia cyanophylla) and agro-industrial by-products (e.g. olive cake, bran etc. conserved in the form of feed blocks or pellets). It has a very shallow anoestrous, the intensity of which is dependant upon nutrition conditions rather than day length as temperate breeds. Productive and reproductive performances of late pregnant-early suckling, pre-mating ewes and also rams of this breed are not affected when some alternative feed resources replace common feedstuffs which are expensive and cannot afford regularly to smallholders. In brief, the merits of the Barbarine sheep in the production systems and other main adaptive mechanisms of this breed are discussed in this paper. The prospective of Barbarine sheep husbandry in the system dynamics, climate change and the evolution of the socioeconomic context are also envisaged.

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

Cited by 22 publications

References 29 publications

Short oestrous cycles in sheep during anoestrus involve defects in progesterone biosynthesis and luteal neovascularisation

Short oestrous cycles in sheep during anoestrus involve defects in progesterone biosynthesis and luteal neovascularisation

Male-induced short oestrous and ovarian cycles in sheep and goats: a working hypothesis

Merits of the fat-tailed Barbarine sheep raised in different production systems in Tunisia: digestive, productive and reproductive characteristics

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