Factors Affecting Function of Induced Corpora Lutea in Postpartum Anestrous Ewes

Gs, Lewis; Aw, Lishman; Rl, Butcher; Dailey, R. A.; Ek, Inskeep

doi:10.2527/jas1981.5251122x

Cited by 15 publications

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“…There were no differences between responses to rams only and rams plus 50/ag of LHRH, in the proportions of ewes with corpora lutea on d 10 or on d 17 or 24, the proportion of ewes lambing by 200 d after treatment, or the average interval from treatment to lambing for those ewes that did lamb by 200 d (table 2). The number of ewes forming corpora lutea in response to treatment may have been underestimated by measuring progesterone on d 10, because some corpora lutea formed after either introduction of rams (Oldham and Martin, 1978/79;Signoret, 1980;Knight et al, 1981) or in response to LHRH (Haresign et al, 1973;Crighton et al, 1975;Lewis et al, 1981) continued to cycle, progesterone would be high on d 17 or 24 and indeed, proportions of ewes with elevated progesterone on one of these days were higher than on d 10.…”

Section: Resultsmentioning

confidence: 99%

“…Luteinizing hormone releasing hormone (LHRH), as a single injection (Foster and Crighton, 1974), or in small repeated doses (Crighton et al, 1975), can induce formation of corpora lutea during seasonal and postpartum anestrus. After a single dose of LHRH, the corpus luteum usually is small and has a short life span and a low level of function (Lewis et al, 1981;McNeilly et al, 1981, Ainsworth et al, 1982. After treatment with progestogens,…”

Section: Introductionmentioning

confidence: 99%

“…59, No. 2, 1984 life span of corpora lutea may be normal or variable (Lewis et al, 1981). Fertility at induced estrus was nil when ewes received LHRH after 5 or 14 d of progesterone and a low dose of estradiol-17~ .…”

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confidence: 99%

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

Gómez-Brunet

Inskeep

1984

Journal of Animal Science

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Two methods of induction of ovulation were examined in Manchega ewes that were in postpartum anestrus during the nonbreeding season. The experiment was of 2 X 2 X 3 factorial design. The methods compared were introduction of rams and this treatment plus an im injection of 50 micrograms luteinizing hormone releasing hormone (LHRH) at the time rams were introduced. Variations in response due to month of treatment (April, May or June) and interval from lambing to treatment (1, 2 or 3 mo) and their interactions with type of treatment were examined. Responses studied were proportions of ewes showing increases in plasma progesterone at (a) 10 d or (b) 17 or 24 d post-treatment, or lambing by 200 d post-treatment, and interval from treatment to lambing for ewes that did lamb by 200 d. The formation of a corpus luteum was determined by concentrations of progesterone in plasma; a positive response was considered to be a concentration greater than .5 ng/ml (baseline values averaged .1 ng/ml). Overall, there was no benefit of LHRH above the response to introduction of males only, in any trait examined. There was a significant interaction of treatment with month of treatment on the proportion of ewes forming corpora lutea by 17 or 24 d after initiation of treatment. This proportion was lower in June (38 vs 66% in April and 82% in May) for ewes receiving LHRH, but did not differ among months (61 to 68%) for ewes exposed to males only.(ABSTRACT TRUNCATED AT 250 WORDS)

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

Gómez-Brunet

Inskeep

1984

Journal of Animal Science

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“…However, in contrast to the endocrine environment of the post-partum period, which is associated with high circulating concentrations of (Lewis et al, 1981;Troxel & Kesler, 1984), it is unlikely that the short-cycle corpus luteum produced in the prepubertal or anoestrous sheep is exposed to abnormally high levels of PGF-2a. It is more likely that this premature, but uterine-dependent, luteolysis may be due to an increased sensitivity of the tissue to the tonic concentrations of uterine luteolysin and/or inadequate luteotrophic protection (Keisler et ai, 1983).…”

Section: Discussionmentioning

confidence: 99%

“…Various factors have been suggested as being the cause of abnormal luteal function in the shortcycle corpus luteum and one of these has been the action on the corpus luteum of a luteolytic or *Reprint requests to Dr M. G. Hunter. antiluteotrophic agent (Lewis et al, 1981;Keisler eia/., 1983;Troxel & Kesler, 1984). The exposure of the induced corpus luteum to high endogenous levels of PGF-2a has been shown, at least in part, to be the causative factor in the premature regression of the short-cycle corpus luteum in the postpartum cow (Troxel & Kesler, 1984) and ewe (Lewis et al, 1981) when concentrations of the luteolysin are elevated after parturition. While levels of PGF-2a remain basal throughout the natural cycle, the normal demise of the corpus luteum at the time of luteal regression is caused by the increased pulsatile secretion of PGF-2a by the uterus (McCracken et al, 1984).…”

Section: Introductionmentioning

confidence: 99%

Effect of hysterectomy on the short life-cycle corpus luteum produced after GnRH-induced ovulation in the anoestrous ewe

Southee¹,

Hunter²,

Law³

et al. 1988

Reproduction

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Anoestrous Romney Marsh ewes were treated with small-dose (250 ng) multiple injections of GnRH. Ewes in Groups 1 and 3 were hysterectomized 2 weeks before treatment, while those in Groups 2 and 4 were intact controls. Groups 1 and 2 were primed with progesterone (+P) and treated with 2 h injections of GnRH (250 ng) for 36 h, while Groups 3 and 4 were not pretreated (-P) but were given 2 h injections of GnRH (250 ng) for 18 h. Both treatment regimens were terminated with a bolus injection of GnRH (125 micrograms), given to synchronize the timing of the LH surge and subsequent luteal progesterone production. The plasma progesterone profiles of 5/5 animals in Group 2 (+P controls) and 2/5 animals in Group 4 (-P controls) were indicative of normal luteal function, while the remaining 3/5 animals in Group 4 produced plasma progesterone profiles typical of abnormal luteal function. However, in all the hysterectomized animals (Groups 1 and 3) peripheral plasma progesterone concentrations rose to reach a mean peak value of 1.3 ng/ml plasma on Day 8 which was maintained in all animals irrespective of progesterone pretreatment. The absence of a fall in progesterone concentrations precluded the identification of any animal in Group 4 showing abnormal luteal function. It was also noted that, after hysterectomy, although the corpus luteum was maintained, it was with reduced secretory capacity. The prevention of the expected proportion (70%) of -P animals from displaying a decline in plasma progesterone concentration after hysterectomy provides firm evidence that the uterus is involved in the premature regression of the short-cycle corpus luteum.

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Does exogeneous progestogen alter the relationships among PGF2α, 13,14-dihydro-15-keto-PGF2α, progesterone, and estrogens in ovarian-intact ewes around the time of luteolysis?

1994

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Factors Affecting Function of Induced Corpora Lutea in Postpartum Anestrous Ewes

Cited by 15 publications

References 0 publications

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

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

Effect of hysterectomy on the short life-cycle corpus luteum produced after GnRH-induced ovulation in the anoestrous ewe

Does exogeneous progestogen alter the relationships among PGF2α, 13,14-dihydro-15-keto-PGF2α, progesterone, and estrogens in ovarian-intact ewes around the time of luteolysis?

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