Effet de la présence du mâle sur les mécanismes de reproduction chez la femelle des mammifères

Signoret, J.P.

doi:10.1051/rnd:19800305

Cited by 20 publications

(8 citation statements)

References 25 publications

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“…This suggests that this level of proges¬ terone may not be sufficient to block the secretion of LH after introduction of the male (see Poindron et al, 1980), and the subsequent secretion of oestrogens may thus induce rapid luteolysis and oestrus. This shortening of the length of the oestrous cycle has already been observed in rodents (review of Signoret, 1980). However, the present results need to be confirmed because the records before introduction of males are not sufficiently precise to permit definition of the exact stage of the oestrous cycle for each female and I cannot be sure that for some unknown reason the cycles were not previously synchronized.…”

Section: Discussionmentioning

confidence: 54%

Effect on oestrus and ovulation of exposing creole goats to the male at three times of the year

Chemineau¹

1983

Reproduction

129

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The characteristics of the oestrous and ovarian cycles of local goats were studied over 2 years, on 96 females in March, 60 in July and 100 in November. After 3 weeks of separation between sexes, the females with inactive ovaries were identified and harnessed males were introduced. Detection of oestrus was undertaken daily and the date and rate of ovulation were checked at laparoscopies. The proportion of females with non-cyclic ovaries before the mating period varied according to the season and whether the females were nulliparous or suckling. Among the females with inactive ovaries before the mating period, 97% ovulated 2 . 8 days after the introduction of males; 68% of these initial ovulations were accompanied by oestrus and 76% resulted in short luteal phases (5 . 3 days) followed by a second ovulation accompanied by oestrus 89% of the time. The proportions of initial ovulations with oestrus and of initial ovulations followed by a short luteal phase were in linear relationship with the proportion of females with non-cyclic ovaries before the mating period. For the females with cyclic ovaries before the mating period, the distribution of first oestrus during the 8 days after the introduction of males was significantly different from the expected uniform distribution. A possible luteolytic action of teasing was suspected. The fertility of females in all groups was high (greater than 79%). Litter size was not different for non-cyclic and for cyclic females.

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Section: Discussionmentioning

confidence: 54%

Effect on oestrus and ovulation of exposing creole goats to the male at three times of the year

Chemineau¹

1983

Reproduction

129

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“…Rams do not need to be in physical contact with the females to induce ovulation (Watson & Radford, 1960). Induction of ovulation could be mediated by the sense of smell (Morgan, Arnold & Lindsay, 1972) or could involve a complex of signals (Signoret, 1980). Furthermore, during oestrus itself, the presence of the male reduces markedly the duration of the sexual receptivity and hastens ovulation by advancing the timing of the ovulatory LH discharge (Lindsay, Cognie, Pelletier & Signoret, 1975).…”

Section: Interruption Of Seasonal Anoestrus By Teasingmentioning

confidence: 99%

Control of seasonal reproduction in sheep and goats by light and hormones

Thimonier¹

2019

Proc

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Seasonal variations of reproductive ability have been demonstrated in male and female sheep and goats. For the female, there is a distinct breeding season. Whilst there are large breed differences in the duration of the sexual season, oestrous cycles generally start when daylength is decreasing and end when daylength is increasing. In some breeds, ovulation without oestrus occurs during the non-breeding season. Although males are able to mate all the year round, seasonal variations occur in the weight of the testis and seminal vesicles and in the fructose concentration of the seminal vesicles. Sexual behaviour and semen characteristics also show seasonal variations. These seasonal variations in males and females are related to hormonal levels. FSH and LH concentrations in the pituitary are reduced to 50% during the non-breeding season. In the peripheral blood, LH concentrations vary throughout the year whilst prolactin concentrations follow the pattern of daylength. Steroid hormones and their feedback actions at the hypothalamo-pituitary axis play a role in the regulation of seasonal reproduction. Three different ways are proposed to overcome these seasonal variations. (1) Males can be introduced into a flock of females before the onset of the breeding season. This leads to induction of ovulation and oestrus, although the first ovulation is frequently followed by a short luteal phase. Teasing does not necessitate contact or sight and is only effective after a period of isolation of the females from the males. (2) Oestrus and ovulation may be induced during the anoestrous period by hormonal treatments. Inducers of LH release have to be associated with a progestagen treatment; PMSG is still the most efficient inducer of LH release. Artificial insemination is useful in this context to avoid subfertility due to seasonal variations of the male. (3) The period of reproduction may be controlled by artificial light regimens. There is a photoinducible period in the circadian cycle of the ewe and it may soon be practical to breed out of season by timed exposure of ewes to short periods of light during the normal hours of darkness. Reproduction in wild animals is often linked to the seasons to ensure that the young are born at a time which maximizes their chance of survival. In domestic animal reproduction, however, seasonality of breeding is a limiting factor because farmers can provide additional food during periods when natural food is short and build shelters to protect the mother and young from the elements. A knowledge of the biological mechanisms determining seasonality is therefore important for the management of domestic sheep and goats.

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“…Many authors have decorticated the short, medium and long-term response to the male effect conducing to a rationalisation in the understanding of female responses (see reviews in sheep [4][5][6][7], in goats [8][9][10]). However, to our knowledge, in spite of these important advances, the general mechanism to explain the existence of an abnormal (i.e.…”

Section: Introductionmentioning

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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Effet de la présence du mâle sur les mécanismes de reproduction chez la femelle des mammifères

Cited by 20 publications

References 25 publications

Effect on oestrus and ovulation of exposing creole goats to the male at three times of the year

Effect on oestrus and ovulation of exposing creole goats to the male at three times of the year

Control of seasonal reproduction in sheep and goats by light and hormones

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

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